if function in cell arrays

Hi everyone,

I try to use to use the if function in cell arrays. If I have A that is 2x100 cells and each cell contains a 6x1 vector. I need to set the following constraint:

for k=1:2
for t=1:100
   if A{k,t}(:,1)<-1;
        A{k,t}(:,1)=-1;
    elseif A{k,t}(:,1)>2;
        a{k,t}(:,1)=2;
end;
end;
end;

This code does not deliver an error. However, it doesn't do what I aim at. It should go on each cell and check the each value of the vectors have a value over or lower than the if statements.

Thanks in advance

Answer 1

[the cyclist]

There are a couple issues with your code. The main issue is that the line

A{k,t}(:,1)<-1

will have a vector output, and therefore the if statement is not doing what you expect. (It would have to be true for every value in the vector, to trigger the if.)

A more straightforward way to do this is as follows:

for k=1:2
for t=1:100
   A{k,t} = max(A{k,t},-1);
   A{k,t} = min(A{k,t}, 2);
end
end

which compares each element of the vector to the threshold value, and replaces it if necessary.

This same operation can be done very compactly, eliminating the for loops completely, with the cellfun function instead:

A = cellfun(@(x)max(x,-1),A,'UniformOutput',false);
A = cellfun(@(x)min(x, 2),A,'UniformOutput',false);

You can even collapse this into a one-liner:

A = cellfun(@(x)min(2,max(x,-1)),A,'UniformOutput',false);

but what you are doing starts to get a little "obfuscated".

(The for loop seems to be the faster method, though, in the limited testing I did.)

[gsourop]

Thanks a lot! I've started working on cell arrays to create a more compact and fast way for the first steps of my code, but then it has started getting more comfusing than I expected.

[the cyclist]

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