# How to write a program to draw a triangle of stars in MATLAB?

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Ali Salim on 20 Mar 2015
Commented: rohit kumar on 15 Oct 2018
I have a exam and don't know how to write a program to draw a triangle of stars, for example :
*
**
***
****
*****
And also flip upside down, for example :
*
**
***
****
*****
And also in the form of isosceles triangle, for example :
*
***
*****
*******
And also in the form of a specific, for example :
*
***
*****
*******
*****
***
*
rohit kumar on 15 Oct 2018
For r=1:4 Forc=1:r fprintf('*'); end fprintf('\n) end

Image Analyst on 20 Mar 2015
Hint:
string = ' '; % 5 spaces.
index1 = 2;
index2 = 4;
string(index1:index2) = '*';
fprintf('%s\n', string);
You need to figure out what index1 and index2 are for the various lines you want to print out.
Jorge Rocha on 5 Jun 2017
But how can I make the third one? (equilateral).

Konstantinos Sofos on 20 Mar 2015
Hi,
For the first
x = [];
for i = 1 : 5
x = strcat(x,'*');
disp(x)
end
for the second
x = [];
for i = 1 : 5
x = strcat(x,'*');
s = [blanks(5-i) x];
disp(s)
end
for the third, the pyramid
x = [];
for i = 1 : 5
x = strcat(x,'*');
s = [blanks(5-i) x];
disp([s fliplr(s)])
end
Image Analyst on 26 Sep 2016
It's to make an x that you can append to. If you don't do that in advance, then what happens when it gets to this line:
x = strcat(x,'*');
It needs to take an already existing x and add a * to it. But if you didn't assign null to x, there is no x to add a star to. So even though x is initialized to null, it's really still there, and we can append stuff to it.

Kunal Kabi on 3 Jun 2017
For printing in this order
*****
***
**
*
Use this code'
clc;
clear all;
close all;
n=input('Enter n=');
for i=n:-1:2
for j=i-1:-1:1
fprintf('*');
end
fprintf('\n');
end