## IF Condition in Wolfram Mathematica

The syntax is as follows

xxxxxxxxxxIf[condition, what to do if true, what to do if false]

Some examples

#### Example 1. Simple command

xx = -3;If[x<0, -x, x]3

#### Example 2. If condition in a function

abs[x_]:=If[x<0, -x, x]abs/@{-3, 2, 0, -2}{3, 2, 0, 2}

## For in Wolfram Mathematica

The syntax is as follows

For[start, test, inc, what to do]

Some examples

#### Example 1. Simple Loop

xxxxxxxxxxFor[i=0, i<4, i++, Print[i]]0123

#### Example 2. Another simple loop

For[i=10, i>0, i--, Print[i]]10987654321

#### Example 3. Print list

a={10, 3, 9, 2}For[i=1,i<5,i++,Print[a[[i]]]]10392

## 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

## 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}]

### ListPlot

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

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

Example

ListPlot[{1, 3, 5}]

### 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}]

### 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}]