MATLAB Scripts

Scripts Introduction

Matlab Script represents some programs and is executed like we execute command in the command window of Matlab’s environment. Matlab script is also defined as a sequence of commands; using the ‘edit’ command in Matlab, we create scripts directly by selecting option from the menu bar. Variables which are created during each session in a script are visible in the workspace section and can be accessed from the command window till we terminate the session. We must save it in the current directory on the Matlab path to execute and run any script file. ‘.m’ extension is used to save scripts in Matlab and referred to as "M-files".

Example:

here p and b1 are added and stored in variable s to use it further.

p = 5; b1 = 7;
s = p + b1
d2 = s + sin(b1)
e3 = 5 * d2
f1 = exp(-d2)

output:

When the above script file is saved, and executed from command line of Matlab, it produces the following output -

s =  12
d2 =  12.657
e3 =  63.285
f1 =    3.1852e-06

What is a script?

Scripts are the difficult kind of program document. For computerizing a progression of MATLAB® orders or commands, scripts are helpful. For example, calculations that you need to perform more than once from the command line or arrangement of commands you need to reference.

How to create a script?

There are two ways creating a script

1. using the ‘edit’ command in Matlab command line

2. We can also create scripts directly by selecting option "new script" from the home menu bar.

Basic functions

Functions

Edit(): to edit or create new files.

Grabcode(): to extract a Matlab code file from file published.

Input(): to initiate a request user input from user.

Publish(): to generate a new view of MATLAB file.

Snapnow(): To take snapshot of image in published document.

Let us understand through examples

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1.edit

We are Creating two new files in a new folder called "newmydir".

In new directory called "newmydir" file, is created using a character vector. Next moment a dialog box then appears, if you want to create newmyscript.m. Then we open tests/newmyscript.m.

mkdir newmydir
edit newmydir/newmyscript.m

Create a second file using a string. Click Yes to create and open tests/new_script2.m

t = "newmydir/newmyscript2.m";
edit(t)

2. input

p = input(promts user) this waits for the user or programmer to enter a value and waits for user to click return key . The user or programmer can enter any expressions like rand(4),ones(2).

• If the Return key is pressed by user then without entering anything, then an empty matrix is returned.

• If an invalid expression is entered at the prompt, then an relevant error message is displayed, and then the prompt is redisplayed again to the user.

Example:

prompt = 'enter the original value please? ';
p = input(prompt)
o = p*20

Output:

3.publish

publish generates a temporary view of the file passed as argument to the function publish() and output is generated as an HTML file format that can be helpful for many purpose like sharing. The HTML file is saved by publish and a file is saved and creates a file named html in subfolder. The html file is located in subfolder is the location of file.

Example:

Filename1 = fullfile(matlabroot,'help','techdoc','matlab_env','examples','fourier_demo2.m');
copyfile(filename,'.','f')
%publish function to run the example and generate an HTML view of the example. 
publish('fourier_demo2.m');
web('html/fourier_demo2.html')

Output:

4.grabcode

grabcode function copies the code from the HTML file (mentioned filename) and then it tries to paste it in the Editor. To get MATLAB code from any internet published files use grabcode, when no availability of the source code is not ready. In MATLAB, code appears as HTML comments at the last of filename from the file mentioned.

Example:

mycode = grabcode('my_sine_wave.html')

Output:

5.snapshot

This function takes snapshot of the image in published document for later inclusion use.

We will look out the following example to understand better.

Example:

%% we are Scaling magic Data and viewed as Image
for o=1:4
    imagesc(magic(o))
end
publish('loopIterations.m')
web('html/loopIterations.html')

Output:

Basic programs

1.Random numbers script file

We have written the code with explanation in the comments embedded in the code

Steps followed in the example:

1. we are first Initializing the number of columns for representation.
2. we are also Initializing the number of rows for representation.
3. we are now defining the bins for the histogram presentation.
4. we are using the ‘Random number generator’ to generate random values for representation.

Example:

Code:

Colno= 4000;
%we are Initializing the number of columns for representation
Rowno = 1;
%[we are Initializing the number of rows ]
bins = Colno/100;
%[we are Defining the bins for the following presentation]
rng(now);
% create random values for representation]
P = 100*rand(Row, Col);
histogram(P, bins)

2.To draw a sphere, we will create a script file

Steps to draw a sphere in Matlab environment, this example:

1.To create the new script we use ‘edit’ command

2.Next we build the logic of sphere to write a Matlab code.

Example:

Code explanation:

edit spherediag

[ The command ‘edit’ is used to create new script in the directory named ‘spherediag’]

 [e, d, c] = sphere;

[we are creating a unit sphere]

Rad = 2;

[the radius of the sphere is initialized]

Surf (e * Rad, d * Rad, c * Rad)

[Adjusting the dimensions of the required sphere]

axis equal

[Making the scale of each axis common] [this file is saved as .m extension]

Next, run this script file for executing, only the name of the file is typed in the command window as follows:

spherediag

code

edit drawSphere
[e, d, c] = sphere;
Rad = 3;
surf(e * Rad, d * Rad, c * Rad)
axis equal

Output:

3. To Plot the Graph a=p² 

Here we are initializing p and obtaining a graph which is equal to this equation a=p².

We have added title to our graph "Graph of a=p^2", also we have added two other labels such as blabel('p') and alabel('a') to make our graph look more appealing. We have used this commands to add more characteristics to the existing above plot.

Code:

p = -1:0.1:1
 a= p.*p
 plot(a,p)
title('Graph of a=p^2')
 blabel('p')
alabel('a')

Output:

p =
  Columns 1 through 15
   -1.0000   -0.9000   -0.8000   -0.7000   -0.6000   -0.5000   -0.4000   -0.3000   -0.2000   -0.1000         0    0.1000    0.2000    0.3000    0.4000
  Columns 16 through 21
    0.5000    0.6000    0.7000    0.8000    0.9000    1.0000
a =
  Columns 1 through 15
    1.0000    0.8100    0.6400    0.4900    0.3600    0.2500    0.1600    0.0900    0.0400    0.0100         0    0.0100    0.0400    0.0900    0.1600
  Columns 16 through 21
    0.2500    0.3600    0.4900    0.6400    0.8100    1.0000

Conclusion

Scripts in Matlab comprise of a grouping of commands or orders which together constitute as a program, and by calling their file name from a different command window the scripts are executed. While making a content, we should save it as .m extention, we refer this as M-files and keep the record name same as the name of the content.