Wednesday, November 14, 2018

If and For in Wolfram Mathematica (with examples)

IF Condition in Wolfram Mathematica

The syntax is as follows

Some examples

Example 1. Simple command

Example 2. If condition in a function

 

For in Wolfram Mathematica

The syntax is as follows

Some examples

Example 1. Simple Loop

Example 2. Another simple loop

Example 3. Print list

 

Monday, November 5, 2018

How to Easily Generate Big File

I had difficulty in finding any large text file. In Google, some of them suggest to download from wikimedia dump and some of them from gutenberg project. However, the following steps are a lot easier than going to all the menus in either wikimedia or gutenberg.

Enter any small text file

In the first step, just enter any small text file. For example:

$ echo 'arwan ahmad khoiruddin' > mytext.txt

Merge the text into big file

Next, you can merge the text into big file. Here's how

$ cat mytext.txt mytext.txt mytext.txt > merged.txt

The content of file merged.txt will be

arwan ahmad khoiruddin arwan ahmad khoiruddin arwan ahmad khoiruddin

So, if you want to create big file, you can just repeat the cat as many as possible. For example

$ cat mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt mytext.txt > merged.txt

Enjoy

Wednesday, October 17, 2018

Introduction to Wolfram Mathematica

Free-form inputs

To compute, press SHIFT + ENTER

In[1]:= 3 + 9 SHIFT + ENTER

Out[1]:= 12

To suppress output, add ; after the line

In[1]:= 3 + 9; SHIFT + ENTER -> no output

You can execute multiple lines at once

In[1]:= a = 2

b = a + 2

c = b ^ 3 SHIFT + ENTER

Out[1]:= 2

Out[2]:= 4

Out[3]:= 64

Starting from now, when we have output, it means that in the end of the previous line, we press SHIFT + ENTER.

To get the most recent output, use %

In[1]:= 3 + 9

Out[1]:= 12

In[1]:= % + 5

Out[1]:= 17

Basics in Programming

Variable

A variable starts with letters. If you want, you may add numbers into the variable name. It is much better if you start the variable name with lowercase

In[1]:= myVariable123 = 2

Out[1]:= 2

Please notice how I join the two words and the number into a single word. If you put space between the variable name, it will indicate multiplication

In[1]:= x = 3;

5 x x

Out[1]:= 45

To clear the variable, use Clear function

In[1]:= x = 2

Out[1]:= 2

In[2]:= 2 x

Out[2]:= 4

In[3]:= Clear[x]

In[4]:= 5 x x

Out[4]:= \(5x^2\)

Conditional Statement

The if contains three parts i.e. test, then (what to do if true), and else (what to do if false). The syntax is as follows

If[test, then, else]

Examples

In[1]:= If[5<8, Print["5 is less than 8"], Print["5 is more than 8"]

5 is less than 8

List

List of items are indicated by { ... }

In[1]:= {1, 2, 3} * 2

Out[1]:= {2, 4, 6}

The index of the list starts from 1

In[1]:= {3, 8, 2, 9}[[3]]

Out[1]:=2

Loop

The syntax used for the loop in Mathematica is as follows

For[start, test, incr, body]

start indicate the condition when the loop is started (initialization)

test indicate the condition to check during the loop

incr indicate the increment happen on each loop

body indicate the operation done during the loop

Example:

In[1]:= For[i=0, i<4, i++, Print[i]]

0

1

2

3

If you want to add more command on each section, separate the command using semicolon ;

Example

In[1]:= For[i = 0, i < 4, i++, Print[i]; Print["hello"]]

0

hello

1

hello

2

hello

3

hello

Data Visualisation

Plot

You can plot single function using the following command

Plot[f, {x , \(x_{min}\) , \(x_{max}\) }]

Example

In[1]:=Plot[Sin[x], {x, 0, 6 Pi}]

If you want to plot more than one functions, use list in the functions

Plot[{f1, f2, ... fn}, {x , \(x_{min}\) , \(x_{max}\) }]

Example

Plot[{Sin[x], Cos[x]}, {x, 0, 6 Pi}]

Screen-Shot-2018-10-17-at-6-32-10-PM

ListPlot

ListPlot function can be used to plot points. The syntax is as follows

ListPlot[{y1, y2, ... yn}]

Example

ListPlot[{1, 3, 5}]

Screen-Shot-2018-10-17-at-6-35-02-PM

ListLinePlot

ListLinePlot can be used to plot a line through the points. The syntax is as follows

ListLinePlot[{y1, y2, ... yn}]

Example

ListLinePlot[{1, 3, 5, 8}]

Screen-Shot-2018-10-17-at-7-01-41-PM

Manipulate Commands

Manipulate is used to see the changes in the output when the input is changed

Example

Manipulate[Plot[Sin[a x], {x, 0, 6}], {a, Pi, 3 Pi}]

Screen-Shot-2018-10-17-at-7-06-55-PM