For loop with if statement!

Here is the samplf of what i am trying to do-

clear all;
clc;
 
s = [1 2 3; 4 0.5 1; 1.3 2 1; 1.5 1.6 2.8]
 
a(1,:,:)  = [ 1 2 3 ; 4 5 6; 7 8 9;10 11 12]
 
a(2,:,:)  = [ 11 12 13 ; 14 15 16; 17 18 19;110 111 112]
 
a(3,:,:)  = [ 111 112 113 ; 114 115 116; 117 118 119;1110 1111 1112]
 
dd= []
for i = 1:size(a,1)
    for j = 1:size(a,2)
        for k = 1:size(a,3)
            if s(j,k)>1.5
                dd(:,:) = double(a(:,j,k));
            else
            end     
        end
    end
end
 
%Expected Answer dd = [2 3 4 8 11 12; 12 13 14 18 111 112;112 113 114 118 1111 1112];

Can anyone tell me how to get the expected answer, i created this sample to understand the problem with some simplicity.

[Ahmed Zankoor]

Firstly, you get an assignment error for matrix a. But it works if you initialize the matrix

a = zeros(3,4,3);
a(1,:,:)  = [ 1 2 3 ; 4 5 6; 7 8 9;10 11 12]
 
a(2,:,:)  = [ 11 12 13 ; 14 15 16; 17 18 19;110 111 112]
 
a(3,:,:)  = [ 111 112 113 ; 114 115 116; 117 118 119;1110 1111 1112]

The second part is not clear at all.

• a(:,j,k) is a 3*1 vector, so you can not form dd like your expected answer.
• dd should be initialized so that you can assign different values at differnt positions.

Answer 1

[the cyclist]

It does not give the expected answer, but using

dd = [dd double(a(:,j,k))];

instead of

dd(:,:) = double(a(:,j,k));

is a step toward what you are expecting, and maybe is enough for you to figure it out?

Also, MATLAB numeric variables are type double by default, so you could just do

dd = [dd a(:,j,k)];

to get the same result.