MATLAB Answers

## I want to randomly have numbers added to a matrix

Asked by Daniel Gray

### Daniel Gray (view profile)

on 11 Jul 2017
Latest activity Answered by Image Analyst

### Image Analyst (view profile)

on 11 Jul 2017
I have a 300x300 zeros matrix and I want to have numbers between 0 and 1 (inclusive) randomly placed amongst the matrix, the numbers can be repeated (and ideally will be repeated completely randomly). Any help would be great.

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## 3 Answers

Answer by KSSV

on 11 Jul 2017
Edited by KSSV

### KSSV (view profile)

on 11 Jul 2017

A = round(rand(300,300)) ;
or
A = randi([0 1],300,300)

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### Star Strider (view profile)

Answer by Star Strider

### Star Strider (view profile)

on 11 Jul 2017

Use the randi function:
M = randi([0 1],300);

Daniel Gray

### Daniel Gray (view profile)

on 11 Jul 2017
Hi, this randomaly places 0's and 1's, is there a way to randomly places numbers between 0 and 1 inclusively?
KSSV

### KSSV (view profile)

on 11 Jul 2017
That case you should use rand
Jan

### Jan (view profile)

on 11 Jul 2017
X = rand(300, 300);
KSSV and Star Strider have suggested randi and rand already. Although the code did not solve your problem completely, the hints are useful already: Read the documentation of the suggested commands to find out, how to use them such, that it satisfies your need. The "See also" lines on the bottom of the docs are very valuable.
I suggest to use the forum not only as a service for complete solutions, but to consider all details mentioned here to improve your own Matlab skills.
In German this is called "mitdenken", but I cannot translate this to English. It doubles the power of the given answers. :-)

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### Image Analyst (view profile)

Answer by Image Analyst

### Image Analyst (view profile)

on 11 Jul 2017

This will do it:
% Create a matrix of all zeros
m = zeros(300, 300);
% Get locations for random changes
% Define the number of random numbers you want placed.
numRandomNumbers = round(.3 * numel(m)); % For example 30%
% Get their locations, randomly arranged.
linearIndexes = randperm(numel(m), numRandomNumbers);
% Assign random numbers to those locations
m(linearIndexes) = rand(1, numRandomNumbers);
imshow(m)

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