how to optimize 'for' loop in MATLAB

Question

i want optimize some loop code such as below . my code is working with large matrix and must be optimized . please help me .

Example one: Expecting Boolean results:

m=zeros(100,100);
r=rand(100,100);
for i=1:100
    for j=1:100
        if(r(i,j)<0.3 || r(i,j)>0.7)
            m(i,j)=1;
        else
            m(i,j)=0;
        end
    end
end

Example two: Expecting NON-Boolean results

m=zeros(100,100);
r=rand(100,100);
for i=1:100
    for j=1:100
        if(r(i,j)<0.3 || r(i,j)>0.7)
            m(i,j)=0.035;
        else
            m(i,j)=0;
        end
    end
end

Luis Mendo · Accepted Answer · 2015-04-01 19:20:47Z

2

Vectorize:

m = r<0.3 | r>0.7;

This gives a boolean result. You may want to convert m to double: m = double(m);.

edited Apr 1, 2015 at 19:20

answered Apr 1, 2015 at 18:35

Luis Mendo

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2 Comments

Reza Ghanami Over a year ago

its good but if we wont boolean answer,what we must do? for example if m(i,j)=.035 insted of m(i,j)=1?

Setsu Over a year ago

@RezaGhanami m * 0.035?

Community · Accepted Answer · 2017-05-23 11:56:52Z

0

Example 1: Luis Mendo's answer

r=rand(100,100);
m = r<0.3 | r>0.7;

Example 2:

m(100,100) = 0;
r=rand(100,100);
m(r<0.3 | r>0.7) = 0.035;

edited May 23, 2017 at 11:56

CommunityBot

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answered Apr 2, 2015 at 5:49

Santhan Salai

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