MATLAB #1 - Commands used in MATLAB

These are some basic MATLAB Commands.

Ctrl + c	stop any action in matlab
clc	clear screen
clear	to clear whole workspace (value of any variable in workspace)
clear y	clears variable y
save	save to the file
load	load the saved file
x=5;y=6;	using “;”, code can be written in one line
z=x+5;	this gives value of z as 10
x=5,y=6;	creates two variable
v=z*… 5	v=10*5=50 i.e. Three dots “…” helps to continue the command in anther line.
help [command name] i.e help format	It gives information about command format
format loose	gives one line space between each line
format compact	removes the spacing between lines
format long	gives answer with 15 digits decimal
figure	opens a blank window for plotting (say name is “figure 1”)
close(1)	close the “figure 1” window
close all	close all the opened windows
edit	to open editor
5/2	gives ans = 2.5
sym(5/2)	gives ans = 5/2
up arrow key	to pop up command history
Format bank	To remove scientific display e.g. : 10e+3 will be displayed as 10000

1.            Plotting in MATLAB        

x=[1,2,3]; y=[5,6,4]; plot(x,y);	x and y are vectors and  plot function plots (1,5), (2,6), (3,4) showing the points in a line
Length(x)	it gives ans = 3 because in x vector there are there elements.
plot(x,y,‘*’)	plots points as ‘*’
plot(x,y,’rs’)	plots point with r= red color and s=square shape
Plot(x1,y1,x2,y2)	Plots two functions y1 and y2 on same graph
Legend(‘pt1’,’pt2’)	Index or legend for point1 and point2
grid on	shows gird on the plotted windows
xlabel(‘x-axis’)	shows x-axis as the label of X-axis
ylabel(‘x-axis’)	shows y-axis as the label of Y-axis
title(‘ploting  points’)	shows plotting points as the title of the plot
axis([0,10,2,8])	min_X=0, max_X=10, min_Y=2, max_Y=8 i.e. they are axis limit

2.            plotting BAR CHART

bar(x,y)	plots bar chart

3.            Plotting PIE CHART         

pie([2 4 7 8 7])

each vector elements separated by space give the size of piece of pie chart

4.            Displaying IMAGES IN MATLAB

pic=imread(‘palace.jpg’); image(pic)

pic is a variable. imread() is a function. palace.jpg is filename of image located in the current folder. image() is a function which takes variarble pic as argument.

5. Matrix

y(:,1)	If you define a bidimensional (2D) array y, and you want to access all its elements on the first column
y(5,:)	If you want to access to all the elements of the fifth row:
:	The colon means: take all the elements along the specified dimension

5. integration

>> syms x >> int(sin(x),x,1,5)

it will integrate sinx with respect to x from 1 to 5

6. Writing to .txt file

Fid = fopen(filename, ‘wt’) fprintf(op, text_to_be_written_to_the_file); fclose(op)	e.g. op=fopen(‘average.txt’, ‘wt’) fprintf(op, ‘This text will be written to the file ’) fclose(op)
Wt	Replaces the content of existing file
At	Adds the current content to the previously existing content of file