R : A crash course for programmers - Chapter01

It was an idea for quite some time to write a blog on R, for the benefit of programmers. Basically Sr Managers in the organizations who were programmers or have good coding experience some time in their life.

How can R be used by them easily. The next series of blogs will be on R.

The contents are available in a book form, leave your email in comments and I will mail the book to you. (PDF)
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Chapter 1 Vectors

2.1 Introduction

Unlike in other programming languages in R the following are the differences.

a.    We don’t use the word variables, rather we use the word vectors. A vector is a data structure.

b.    In other programming languages for instances we have numbers (int and floats) and arrays etc. Where as in R everything is an array. So a number is essentially an array with a single element.

Let us take some examples.

> a<-10 span=""> > b<-c span=""> > a [1] 10 > b [1] 10 > class(a) [1] "numeric" > class(b) [1] "numeric"	Vector a is defined as a number, where as b is defined as an array. But both are treated as an array of one number. The class() function determines type of the array. <- a="" and="" assign="" hyphen.="" is="" less="" operator="" span="" than="" the="" to="" value="">
> a[1] [1] 10 > b[1] [1] 10	As a proof that both are the same description we can try to print the first element in the array. Note a also behaves like an array because it is one.

2.2 Operations in R.

R is rich in operators. Operators can evolve to a numeric value or to a logical value. Just as I told earlier all variables are essentially arrays, so a operator works on an array jus like a number.

Look at the following examples.

> a<-10 b="" c="" span=""> > a;b [1] 10 [1] 10 20 30 > a+10;a*10;a^2;a%%3 [1] 20 [1] 100 [1] 100 [1] 1 > b+10;b*10;b^^2;b%%3 [1] 20 30 40 [1] 100 200 300 > b+10;b*10;b^2;b%%3 [1] 20 30 40 [1] 100 200 300 [1] 100 400 900 [1] 1 2 0	The ; can be used to separate multiple commands to be issued in the same row. The arithmetic operators +, - * , / are self explanatory. ^ is for the power of. a^2 here means a2 %% is the modulus operator, it gives the remainder.
> a>10;b>10 [1] FALSE [1] FALSE  TRUE  TRUE	Logical operators are supported as well. >, >=, <. <=, !=. The logical operators return a logical output.

2.3 Name in R.

The elements of a vector are accessed by using integers. The first item is at index 1. R is more interesting in one aspect and that is naming. You can name a vector’s columns. And then you can use those names for accessing the items. Look at the following examples to understand more. Remember any line that begins with a # is treated as a comment.

> sales<-c span=""> > sales [1] 120 190  90 > sales[1] [1] 120 > sales[3] [1] 90	Here the sales vector is defined with three numbers. You can check by entering class(sales) and you get an output NUMERIC. The elements are accessed using numbers 1,2… etc.
> names(sales)<-c an="" ar="" eb="" span=""> > sales Jan Feb Mar 120 190  90	The names function gives names to the columns. Since we have three columns in the sales vector, we give three names. (Jan, Feb and Mar).
> max(sales) [1] 190 > > sales==max(sales)   Jan   Feb   Mar FALSE  TRUE FALSE	The max is an inbuilt function that goes thru the vector (sales) and lists the column that has the max value. When you list the sales vector with sales==max(sales), it gives us a logical vector with TRUE/FALSE values.
> sales[max.sales] Feb 190 > class(sales) [1] "numeric" > class(max.sales) [1] "logical"	Here we create a new logical vector called max.sales. Remember that vector names can have . or _ or lower/upper case characters. The sales[max.sales] is used to display that column that has the TRUE value.

That brings an end to chapter 1.

The next page has some exercises for you to try.

2.4 Exercises

1.     Download the R. Goto the following web site to download R.

a.     https://cran.r-project.org/bin/windows/base/

b.   

c.     Create a folder called c:\R

d.     Install R in this folder.

e.     You don’t need anything else for the time being, There are some good IDE for you to work, one of them is R Studio. You can download it from https://rstudio.com/products/rstudio/download/

f.     Choose the R studio desktop free version and install it in the c:\R folder

2.    Run the R.exe from the C:\R\R-3.6.3\bin, if you installed it in c:\R

a.    You can do all the remaining questions from here. If you use R studio then you can do the exercises from here.

b.   

c.     Increase the size of “Console” window and you can do the exercises from here. If you run R.exe then the screen looks like this

d.    

e.     The back ground is black and fonts are small by default. Right click on the title bar, goto to properties

f.    

g.    You can set the colors and fonts from here.

3.   Questions that you need to do.

a.    You can run the sample code that I used during the chapter to test if you see the same output as the one I have shown.

b.    Declare a numeric vector called train.late with the following (12, 16, 14, 21, 3, 19,9)

c.     Give a heading from Mon to Sun.

d.     Assuming that the numbers are in minutes, find the following

                                          i.    On which day was the train min late

                                         ii.    On which day was the train max late.

                                        iii.    What is the average late in minutes for the train.

                                       iv.    On which days was the train more than 10 minutes late

e.     Find the value of the following equations

                                          i.    32+64

                                         ii.    32+25*4

                                        iii.    3²-(25+16)*12

                                       iv.    Remainder of 100 divided by 9.

f.     Create a nums.list vector with the following numbers 1,2,3,4

g.    Create a nums.list2 with the following numbers 2,4,6,8

h.    Find the following

                                          i.    Nums.list + nums.list2

                                         ii.    Nums.list^nums.list2

                                        iii.    Nums.list2^nums.list

4.  You define x<- span="">

a.    What is the output of sort(x)?

b.    What if you want the output in reverse order (max to min)?

Vijay Mukhi

I read in the news papers of the passing away of the genius Vijay Mukhi. I never got a chance to attend his trainings, but those who attended admired his technical skills.

Knowing something is different and being able to deliver it so that your students ultimately become larger than yourself, is the aim of every trainer. Vijay Mukhi created thousands and thousands of students, via both his training institute as well as the books that he has left.

I 1991, some time, I started reading the C Odyssey, series. The book is so well written. Example by example. Those days (and even today), text books were too much story telling. Concept after concept and no real examples. The C Odyssey, was a paradigm shift. The book was full of examples. Not just examples, but related examples. Short lines of code, related code, and any one could read and master it.

The C Odyssey series looked like this.

The likes of Vijay Mukhi build a foundation for the future. Education is the basis of gowth. He will be missed. Loads of interesting material is available here


Source : Mid Day

Shri Pradeep Kshetrapal

A short story.

The year was 1985, if I am not wrong. The place was Korba in Chattisgarh, India. Those days Chattisgarh had not been formed and so Korba was a part of Madhya Pradesh.  I was in my 11th Standard. We did not have a Physics teacher. A gentleman walks in one day into the class to teach us Physics. He was so mild in his speech, so well mannered, precise in what he wanted to speak, and professional in his approach. He took the first class. We were all speechless. We loved the class, and loved this person.

Our new teacher that day was none other than Pradeep Kshetrapal sir, as used to call him lovingly. His style of teaching was very simple. Take a topic, make it easy, complete it in the class with some real life examples that we could relate. Days, months passed on. We wrote the exams and I am sure every one made a good grade. He called the entire class to his house, after the exams. We had a nice get together and he gave us letter heads with our names printed on it. It was the first time we have customized gifts. It was a nice party.

Then we lost touch, till one day I came to know that he is doing this great work of teaching. He had a channel on youtube from the lessons could be seen and heard. The same style and memories came flashing. I mailed him and he replied. Reading more about him on the net, I came to discover what a gem of person he is.

Read here more about him.
His profile on Google+


Salute Shri Pradeep Kshetrapalji.

The youtube channel is here.

New Year 2015

Wishing a new year 2015.

 

Lesson 9 : Some fun

1729 is known as Hardy Ramanujam Number.  (There is a wiki article here). Reading the article all the way down, I read an interesting part that the Japanese Scientist Masahiki Fujiwara found out.

1729 –> add the numbers and you get 1+7+2+9=19

Reverse 19 and you get 91. 19x91=1729. According to him only 2 more numbers other than 1729 show this property. One is 81 and other is 1458. I decided to write a small piece of code to verify this.

for x=10 to 9999 ' find the sum of numbers first ' reverse this number ' multiply it and you should get the original number     n=x     s=0     while (n>0)         s=s+(n mod 10)         n=int(n/10)     wend 'reverse s, call it rs     if s<10 then         rs=s     else         rs=(s mod 10) * 10 + int(s/10)     end if     if (s*rs = x) then         wscript.echo x     end if    next

 

C:\scripts>nos.vbs //nologo 81 1458 1729 C:\scripts>

And yes there are only 3 numbers.

Lesson 8 : Solution to the question

Question was to modify the code in the last lesson, where

- the comma could be replaced by tab, for making it easy to read

- to add the columns and show the total.

In  the following code, it takes two parameters, first is csv file, and second is col. The same old file is used. The csv file first

C:\scripts\file-io>type sample.csv abcd,12,E_123,300 bcde,13,E_124,301 cdef,14,E_125,302 efgh,15,E_126,303 ghij,16,E_127,304 hijk,17,E_128,305 lmno,18,E_129,306 C:\scripts\file-io>

The output of the program

C:\scripts\file-io>03-addcols-csv.vbs sample.csv 4 //nologo abcd    12      E_123   300 bcde    13      E_124   301 cdef    14      E_125   302 efgh    15      E_126   303 ghij    16      E_127   304 hijk    17      E_128   305 lmno    18      E_129   306 Sum of Col 4 is 2121

And finally the code

Const ReadMode=1 dim fso dim fstext dim txtline dim lines, words dim strword dim Oput dim sums oput=int(wscript.arguments(1)) set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) sums=0 do until fstext.AtEndOfStream         txtline=fstext.ReadLine         strword=split(txtline,",")         sums=sums+int(strword(oput-1))         txtline= Replace(txtline,",", vbTab)         wscript.echo txtline loop wscript.echo " " wscript.echo "Sum of Col " & oput & " is " & sums

What more can be done.

a. You can validate if the column selected exists and if it does exists is it a numeric value.

b. You can check if the csv file passed as a parameter exists in the first place.

Lesson 8 : Working with CSV files

The fun starts working with CSV files.  CSV files are comma separated value, files. Basically that means there are commas between the columns. So who creates them? Almost every application that creates logs, dumps performance data, configuration, etc. Before XML files became the craze CSV ruled the administrator’s world.

Below is a sample CSV file

abcd,12,E_123,300 bcde,13,E_124,301 cdef,14,E_125,302 efgh,15,E_126,303 ghij,16,E_127,304 hijk,17,E_128,305 lmno,18,E_129,306

Let us write a code that can display any column we like. If we pass the parameter 0 (zero) we get the entire file. If we pass a specific number we get that column. If we pass a number more than the columns we show the entire file.

First the code

'Show the selected coloumn Const ReadMode=1 dim fso dim fstext dim txtline dim lines, words dim strword dim Oput oput=int(wscript.arguments(1)) set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) do until fstext.AtEndOfStream     txtline=fstext.ReadLine     strword=split(txtline,",")     if oput=0 or oput>(ubound(strword)+1) then         wscript.echo txtline     else         wscript.echo strword(oput-1)     end if loop

And now the output

C:\scripts\file-io>02-show-contents.vbs sample.csv 0 //nologo abcd,12,E_123,300 bcde,13,E_124,301 cdef,14,E_125,302 efgh,15,E_126,303 ghij,16,E_127,304 hijk,17,E_128,305 lmno,18,E_129,306 C:\scripts\file-io>02-show-contents.vbs sample.csv 1 //nologo abcd bcde cdef efgh ghij hijk lmno C:\scripts\file-io>02-show-contents.vbs sample.csv 2 //nologo 12 13 14 15 16 17 18 C:\scripts\file-io>02-show-contents.vbs sample.csv 3 //nologo E_123 E_124 E_125 E_126 E_127 E_128 E_129 C:\scripts\file-io>02-show-contents.vbs sample.csv 4 //nologo 300 301 302 303 304 305 306 C:\scripts\file-io>02-show-contents.vbs sample.csv 5 //nologo abcd,12,E_123,300 bcde,13,E_124,301 cdef,14,E_125,302 efgh,15,E_126,303 ghij,16,E_127,304 hijk,17,E_128,305 lmno,18,E_129,306 C:\scripts\file-io>

Some exercises for you to try.

1. Suppose we need the sum of a column (like column 2 or 4) then modify the above code so that it works in the following way.

c:\>progname csvfile col

The output should a tab between the cols and not a csv and a sum below.

Lesson 7 : Working with Text files

In our routine as an administrator, we routinely work with text files. Let us try to understand how to work with them.

A usual logic would be

- Open the file, Loop line by line, display the contents (or process them)

Example 1:

In this example, we try to display the contents of the file that is passed as a parameter at the command line. I have not done validations and assume that a file name is already there. You can add three validations, first check if there is an argument. Second check if the file exists. Third check if it is a text file.  I have a sample file called “sample.txt” in the same folder as the program.

Const ReadMode=1 dim fso dim fstext dim txtline set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) do until fstext.AtEndOfStream     txtline=fstext.ReadLine     wscript.echo txtline loop

Let us check the output

C:\scripts\file-io>01-show-contents.vbs sample.txt //nologo The quick fox jumped over the lazy dog. The hare and the turtle were friends in the forest. Early bird gets the worm. C:\scripts\file-io>

Let us make it more useful. At the end, let us say we want to display the total lines in this file.

Const ReadMode=1 dim fso dim fstext dim txtline dim lines lines=0 set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) do until fstext.AtEndOfStream     txtline=fstext.ReadLine     wscript.echo txtline     lines=lines+1 loop wscript.echo "--------------------------------------end of file" wscript.echo "Lines in the file " & lines

C:\scripts\file-io>01-show-contents.vbs sample.txt //nologo The quick fox jumped over the lazy dog. The hare and the turtle were friends in the forest. Early bird gets the worm. --------------------------------------end of file Lines in the file 4 C:\scripts\file-io>

What if we needed the lines and words.

a. Use the split function, it splits a string and returns an array

b. use the ubound function to check how many elements are there in the array, and add 1

Const ReadMode=1 dim fso dim fstext dim txtline dim lines, words dim strword lines=0 words=0 set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) do until fstext.AtEndOfStream     txtline=fstext.ReadLine     strword=split(txtline)     words=words+ubound(strword) +1     wscript.echo txtline     lines=lines+1 loop wscript.echo "--------------------------------------end of file" wscript.echo "Lines in the file " & lines wscript.echo "Number of words   " & words

Sample Output of the same file

C:\scripts\file-io>01-show-contents.vbs sample.txt //nologo The quick fox jumped over the lazy dog. The hare and the turtle were friends in the forest. Early bird gets the worm. --------------------------------------end of file Lines in the file 4 Number of words   23 C:\scripts\file-io>

Let us make it more complete. We do the following changes, we pass the parameter filename with a number, 1=show file, 2=show lines, 3=show words, 4=show all

Code

Const ReadMode=1 dim fso dim fstext dim txtline dim lines, words dim strword lines=0 words=0 dim Oput oput=int(wscript.arguments(1)) set fso=CreateObject("Scripting.FileSystemObject") set fstext=fso.OpenTextFile(wscript.arguments(0),ReadMode) do until fstext.AtEndOfStream     txtline=fstext.ReadLine     strword=split(txtline)     words=words+ubound(strword) +1     if oput=1 or oput=4 then         wscript.echo txtline     end if     lines=lines+1 loop if oput=1 or oput=4 then     wscript.echo "--------------------------------------end of file" end if if oput=2 or oput=3 or oput=4 then     wscript.echo "Lines in the file " & lines end if if oput=3 or oput=4 then     wscript.echo "Number of words   " & words end if

Various Runs

C:\scripts\file-io>01-show-contents.vbs sample.txt 1 //nologo The quick fox jumped over the lazy dog. The hare and the turtle were friends in the forest. Early bird gets the worm. --------------------------------------end of file C:\scripts\file-io>01-show-contents.vbs sample.txt 2 //nologo Lines in the file 4 C:\scripts\file-io>01-show-contents.vbs sample.txt 3 //nologo Lines in the file 4 Number of words   23 C:\scripts\file-io>01-show-contents.vbs sample.txt 4 //nologo The quick fox jumped over the lazy dog. The hare and the turtle were friends in the forest. Early bird gets the worm. --------------------------------------end of file Lines in the file 4 Number of words   23 C:\scripts\file-io>

We build more on this in the subsequent chapters.

Lesson 6: Functions and Procedures (vbscript)

Functions and Procedures make your code modular. They help you to keep repeated statements as blocks of code that can be reused. Both functions and procedures do the same thing, except, Functions can return value. So as a good practice never let your functions have any statements to print(display) or get input from keyboard.

Let your functions take parameters and return the value. How does a function return a value? Function_name=value you want to return. Enough of theory.

This program finds the value of (a+b) squared.

(a+b)² =a² +2ab+b²

‘File-0105-1.vbs (this is file name I have) Function Sq_ab(a,b)     sq_ab=a*a + 2*a*b + b*b End Function Sub Print(str)     wscript.echo str End Sub 'Main program starts here a=int(wscript.arguments(0)) b=int(wscript.arguments(1)) Print("The Square of (a+b) is " & Sq_ab(a,b))

Sample Output

C:\scripts>0105-1.vbs 2 3 //nologo The Square of (a+b) is 25 C:\scripts>0105-1.vbs 7 9 //nologo The Square of (a+b) is 256 C:\scripts>

Exercises for you.

1. Write functions for (a-b)², a²-b², (a+b)³ and so on

Windows Scripting. Lesson 5. Magic Square

A magic square is one where the total of rows, columns and diagonals is the same.

Take a 3x3 magic square.

The Rules are pretty simple. The rule is called top-left rule.

1. Start with 1. Put it in the centre of the 1st row. So 1 is in (1,2) Row 1, Col 2.

2. Goto top left. In this case top is row 0, so top comes to the 3rd row. Left is row 1. So the next number is (3,1).

3. Continue with top left. Top of 3 is 2, left of 1 is 3rd column. So we are in (2,3).

4. Now the top left from 2,3 is 1,2. This place is occupied, you have a 1 there. So you need to go back to original location (2,3). Then come a place down but same column. So from 2,3 we come to 3,3. Put a 4 here. Continue this way.

5. In this case the totals of rows, col and diagonal is 15. Why 15?

6. We use the natural numbers 1 to 9. Sum of 1 to 9 is n(n+1)/2. In this example we have 9x10/2=45. We have 3 rows. So we get 45/3 or 15.

sub Print(str)     wscript.echo str end sub ' Main Program starts from here dim x(3,3) dim y for a=1 to 3     for b=1 to 3         x(a,b)=0     next next x(1,2)=1 a=1 b=2 for y=2 to 9     olda=a     oldb=b     a=a-1     b=b-1     if a=0 then         a=3     end if     if b=0 then         b=3     end if     if x(a,b)>0 then         a=olda         b=oldb         a=a+1     end if     x(a,b)=y next for a=1 to 3     for b=1 to 3         str=str & chr(9) & x(a,b)     next     wscript.echo str     str=" " next

- print procedure makes the printing easy.

- dim, defines an array. In this case it is an array 3 rows x 3 cols. Each value in the array is defined as 0. 1 is put then in the first row and second column.

- for loop rotates eight times for the eight numbers. a and b are the locations needed. We try top left, and if it is occupied (>0), then we go back to the original location and come one col down.

- the for loop then prints the 3 coloumns. Each row is formatted is by adding a tab (chr(9). When you compile and run this program, (magic3.vbs)

C:\scripts>magic3 //nologo         6       1       8         7       5       3         2       9       4 C:\scripts>

 

Can we make a generic version of this program.  Where we can print for any odd number. Since vbscript does not allow to define an array with a variable, I have defined a large array (20,20) and allow to print a magic square. The beauty is you can pass the number as a parameter. If the parameter is even, then we add 1 and make it a odd number. The program is very similar to the previous program.

sub Print(str)     wscript.echo str end sub sz=int(wscript.arguments(0)) if sz mod 2 = 0 then     print "Argument Should be Odd"     print "Changing to odd"     sz=sz+1 end if 'sz=3 dim x(20,20) dim y for a=1 to sz     for b=1 to sz         x(a,b)=0     next next x(1,(sz+1)/2)=1 a=1 b=(sz+1)/2 for y=2 to (sz * sz)     olda=a     oldb=b     a=a-1     b=b-1     if a=0 then         a=sz     end if     if b=0 then         b=sz     end if     if x(a,b)>0 then         a=olda         b=oldb         a=a+1     end if     x(a,b)=y next for a=1 to sz     for b=1 to sz         str=str & chr(9) & x(a,b)     next     wscript.echo str     str=" " next

Sample output.

C:\scripts>magicgen 5 //nologo         15      8       1       24      17         16      14      7       5       23         22      20      13      6       4         3       21      19      12      10         9       2       25      18      11 C:\scripts>magicgen 7 //nologo         28      19      10      1       48      39      30         29      27      18      9       7       47      38         37      35      26      17      8       6       46         45      36      34      25      16      14      5         4       44      42      33      24      15      13         12      3       43      41      32      23      21         20      11      2       49      40      31      22

An exercise for you. Can you use the n(n+1)/2 formula as mentioned earlier and print one line at the end of the program.

Sum of Rows/Col is _______

Like this

C:\scripts>magicgen 5 //nologo         15      8       1       24      17         16      14      7       5       23         22      20      13      6       4         3       21      19      12      10         9       2       25      18      11 Sum of rows/col is      65

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 4–FileSystemObject Contd..

Continuing on FileSystemObject, Let us look at and example to extract the properties of a file. There are some new things introduced in this example

1. SUB. This is for a procedure. you can pass parameteres just like functions but just that you cannot return any values. I have put a simple procedure called Print, that takes a string as a parameter.

2. Parameteres.  You can pass parameteres to a vbscript. Wscript.argument, is where you can see the list.

Sub Print(x)     wscript.echo x end sub set fso=CreateObject("Scripting.FileSystemObject") set f=fso.GetFile(wscript.arguments(0)) print "Path               " & f.path print "Date Created       " & f.datecreated print "Date Last Accessed " & f.datelastaccessed print "Date last modified " & f.datelastmodified print "Drive              " & f.drivedir print "Parent Folder      " & f.parentfolder print "Size (Bytes)       " & f.size print "Type of File       " & f.type

A few examples

C:\scripts>folder.vbs c:\53-Photos\ar-1.jpg Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. Path                       C:\53-Photos\ar-1.jpg Date Created          09/03/2014 19:50:08 Date Last Accessed  09/03/2014 19:50:08 Date last modified  09/03/2014 19:50:08 Drive                      c: Parent Folder          C:\53-Photos Size (Bytes)             66089 Type of File            JPEG Image C:\scripts>folder folder.vbs Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. Path               C:\scripts\folder.vbs Date Created       18/04/2014 00:01:02 Date Last Accessed 18/04/2014 00:01:02 Date last modified 18/04/2014 01:06:49 Drive              C: Parent Folder      C:\scripts Size (Bytes)       491 Type of File       VBScript Script File C:\scripts>

You can try an example to show the file size in MB or GB depending on the size of the file. Or may be list an output like the DIR command.

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 3–Objects

After the basics of variables, Selection and Iteration statements, let us do something useful in real life. We start with the first object FileSystemObject. This gives us access to the filesystem. An essential part of scripting. We may need to create files, modify content, look for their existence. The idea is to make you familiar with using objects as well.

Let us take an example

Set fs = CreateObject("Scripting.FileSystemObject") Set dc = fs.Drives For Each d in dc     wscript.echo d.driveletter Next

Save this script as fsdrives.vbs

Run it

C:\scripts>cscript fsdrives.vbs //nologo C D F C:\scripts>

I have three drives on my laptop. Your machine may have more or less. Let us understand the code.

Line 1 is creating an object of FileSystemObject type. Without this you cannot use what is in this object. An object is contains methods (functions) and variables. The variables may be simple variables or may be collections. Collections are more like an array, you can use a for loop to go through each of the items, and then access the properties of each.

fs is an instance of the FileSystemObject

fs.drives is referencing a property of the FileSystemObject

fs.drives returns a collection of drives.

To loop through it we need a for loop. dc is the drive collections we have used. You have a collections of drives. For each drive there are many properties. We are referencing one of the property called driveletter.

Let us make the above program more richer. We not only need the drive, but also want to know the capacity and free space.

' Main Code Starts here Set fs = CreateObject("Scripting.FileSystemObject") Set dc = fs.Drives s=chr(10) & "Number of Drives " & dc.count wscript.echo s s=string(65,"-") wscript.echo s For Each d in dc     s=d.driveletter & chr(9) & d.path & chr(9) & d.isready     if d.isready then         s=s & chr(9) & d.volumename         s=s & chr(9) & d.filesystem         ts=int(int(int(d.totalsize/1024)/1024)/1024) & " GB"         s=s & chr(9) & ts           ts=int(int(int(d.freespace/1024)/1024)/1024) & " GB"         s=s & chr(9) & ts           ts=int(int(int(d.availablespace/1024)/1024)/1024) & " GB"         s=s & chr(9) & ts            end if     wscript.echo s Next ' We have explored, volumename, filesystem, totalsize, freespace ' availablespace, driveletter, path and isready properties from ' the drives collection. These values are for each drive. ' chr(9) is for tab and chr(10) is for new line ' Anything typed after single quote is a comment. ' space is shown in bytes. change to KB, MB, GB by dividing 1024

Copy and paste the code. Run it.

C:\scripts>cscript fsdrives.vbs //nologo Number of Drives 3 ----------------------------------------------------------------- C       C:      True                  NTFS    421 GB  195 GB  195 GB D       D:      True    LENOVO  NTFS    28 GB    19 GB    19 GB F       F:      False C:\scripts>

That is the output I get. Your challenge would be to fine tune the code further so that the numbers are aligned below each other. On your machine you may see more or less drives and the numbers different.

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 2–Solution Part 2

Fibonacci Series Solution

wscript.echo "Fibonacci Series" x=1 y=1 wscript.echo 1 wscript.echo 1 for a=3 to 15     z=x+y     x=y     y=z     wscript.echo z next

 

Output

C:\scripts>cscript fibo.vbs //nologo Fibonacci Series 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610

 

An interesting video on Fibonacci Series can be viewed here.

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 2–Solution

The following is the solution of the question in the last post. Printing the prime numbers between 1 and 100. This may not be the best logic, yet it gets what to be done. It is more important to develop a timely solution than an untimely one.

wscript.echo "1" wscript.echo "2" wscript.echo "3" for x=5 to 100 step 2     isprime=0     for z=2 to x-1         if x mod z = 0 then             isprime=1         end if     next     if isprime=0 then         wscript.echo x     end if next

and the output

C:\scripts>cscript prime.vbs //nologo 1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Some more examples that you should try

1. List the Fibonacci series – first 15 numbers

2. Find the Square root of any number correct to 4 decimal places. (use Newton’s method)

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 2

In any programming language there are three things we need to learn at the earliest.

1. Types of variable

2. Selection Statements

3. Iteration or Loops

Since ours is a “get ready quick” course. We will only try what we think is essential.

1. Variable.

There are no types of variables. What ever you assign the variable takes that values. Unlike in other programming languages you have int, char, fload, date etc. There is nothing here. You can just put any value in any variable. The upside is variable usage is easy. Same variables can be recycled. The downside is explicit conversions are needed everytime a variable of a specific type is needed.

Assume you have a program with the following

i=5 wscript.echo i i="Programs" wscript.echo i

When you run it there is no error.

 

2. Selection statements.

Keeping it simple.

if <condn> then

<statements>

else

<statements>

randomize i=int(rnd * 10) wscript.echo i if i mod 2 =0 then     wscript.echo "Even Number" else     wscript.echo "Odd Number" end if

randomize – resets the seed, so that you get a real random numbers all the time. rnd generates a random number between 0 and 0.999xxx. The int function converts the output to an integer (we don’t need the decimals). The mod is a operation to find the remainder.

The above program prints either even or odd depending on the random number. In the example the program is saved as third.vbs

C:\scripts>cscript third.vbs Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. 7 Odd Number C:\scripts> C:\scripts>cscript third.vbs Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. 1 Odd Number C:\scripts>third Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. 0 Even Number C:\scripts>cscript third.vbs Microsoft (R) Windows Script Host Version 5.8 Copyright (C) Microsoft Corporation. All rights reserved. 6 Even Number C:\scripts>

3. Iteration or Loops

The most convenient loop is the for – next.

An example

wscript.echo "Program 2" for i=1 to 5         wscript.echo i next wscript.echo "Random Numbers" for i = 5 to 1 step -1         randomize         intnum=rnd         wscript.echo int(intnum*10) next

 

A simple program the prints, from 1 to 5. And then random numbers between 0 and 9.

Program 2 1 2 3 4 5 Random Numbers 1 0 8 2 0

Try this exercise.

Print the first 100 prime numbers.

use the concepts learnt.

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 1

Windows Scripting (the normal shell) for Ex VB Programmers - Lesson 1

Good if you know the old Visual Basic

1. How to write your first script. (lets call this as first.vbs)

1. run cmd.exe

2. create a folder called c:\scripts

3. run notepad first.vbs

4. Save and run this file as follows

5. Try to run the file without using cscript and see what you get

6. This is because by default vbs files are executed using wscript

7. what if you wanted to change the default. Do the following

8. What if you wanted to change back the default to wscript

wscript //H:wscript

-----------------------------------------------------------------end of lesson

Even Browsers can give your location

Yes. If you are on facebook, or for the matter on any web site,  and worry about your privacy, which you should then what to do?.

The first thing that you can or should do is, disable your location. Let your browser not know your location. How do get this done on three main browsers.

1. Firefox. (works on Ver 26)

a. Open a window and type about:config

b. Agree to the warning.

c. Search for geo.enabled and Set it as false. Look in the image.

2. Google Chrome

a. Open a windows and type chrome://settings

b. Click on Advanced Settings

c. Under Privacy click on “Content Settings”

d. Scroll down and choose “Location Setting” and select

3. Internet Explorer

a. goto Tools->Internet Options

Select the “Privacy Tab”

And check the box as shown above.

 

And now surf the internet atleast not worrying about your location is tracked. What next?

Lessons : The honest truth about dishonesty.

On my recent travel I read this book. Very relevant and lots of research gone into it.

 

You can click on the book to goto Amazon.

Dishonesty, that we hardly think about in our daily lives is sometimes very subtle. I look back and find that in my life as well there are cases where it can be seen. For instance taking more than an hour for lunch, or sometimes taking a long tea break. Also the research done in the book gives insights on how we can ensure practices that can reduce dishonesty in our work place.

A worth read.

Cloud Storage. What to look for.

Every one talks cloud. Let us look at Cloud Storage. What it means? You store your data at a third party place. Why? May be lower cost, administration simplification, security, protection etc. All these things encourage us.

Where are the risks? Like all business a cloud business can fail too. What if your cloud company is the single point of failure. What happens then?

a. Your data sits on the cloud. Your cloud provider closes shop. Do you have enough time to get it back? Even you have that time, do you have enough space to get it back. Even if you can get it back will the provider have enough bandwidth for all those who want their data?

b. Suppose you got back the data, you also somehow managed to secure some storage, will your applications work? Who will make changed to them? Can you keep your RPO?

So then what is the solution? May be in a next post.

Bye Bye Altavista

Come 8th July and another search engine altavista is going to leave cyberspace. Altavista has been one of the first search engines, indexing millions of pages. It was a product that too ahead of its time. Some how through companies buying each other, it came with Yahoo. Now Yahoo has decided to stop this product.

Surprising but in my two decades in IT I have started to see even good products reaching their end of life. Have a look at this page as of today.

From 8th July the domain name www.altavista.com will redirect to yahoo.com.

Source : BBC