Asked by ellis langdon
on 13 Feb 2019 at 16:50

Hi

I am currently working on a project with temperature data. The data is stored in a 128 x 64 x 2160 matrix called T.

I have calculated that summer is between index 30:48 and then +72 for the consecutive summer years.

I want to loop through the third dimension and stored this in a new variable ST.

Please see below code I have already made, i'm not too sure where to go after this.

ST=NaN*ones(128,64,30) %Setting up grid

x=0;

for i=30:48;

x=x+1;

ST(:,:,x) = T(:,:,[i:i]); %Looping through third dimension 30:48

end

ST should essentially be 128 x 64 x 30 or 128 x 64 x 540 matrix

Any help would be great, thank you!

Answer by Jan
on 13 Feb 2019 at 16:59

Edited by Jan
on 14 Feb 2019 at 14:48

Accepted Answer

Your loop has 19 iterations. It is not clear, why you expect that the output has a size of 30 or 540 in the 3rd dimension.

[i:i] is the same as the much simpler: i .

A simplified version of your code:

ST = T(:, :, 30:48)

No loop needed. But I do not see, how this could produce a size of 30 or 540.

By the way, this can be simplified also:

ST=NaN*ones(128,64,30)

% Better:

ST = NaN(128, 64, 30)

But it is not useful here, so better omit it.

[EDITED] After the clarifications:

ST = NaN(128, 64, 18, 30); % Pre-allocate

ini = 30;

len = 18;

for k = 1:30

ST(:, :, :, k) = T(:, :, ini:ini + len - 1);

ini = ini + 72;

end

ST = reshape(ST, 128, 64, 540);

% Or:

v = 1:72;

match = (30 <= v & v < 48);

ST = T(:, :, repmat(match, 1, 30));

ellis langdon
on 13 Feb 2019 at 17:11

I am trying to put all of the summer values into the new grid (ST). The summer values are between 30 and 48, which increase annually by 72.

For example the loop will put all the values between 30:48 into ST(:,:,x), after the loop has reached 48, it should go back and increase everyhing by 72 until the ST array has been filled.

I hope that makes sense.

Matt J
on 14 Feb 2019 at 14:53

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## 3 Comments

## Matt J (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/444797-looping-through-3rd-dimension#comment_670944

## ellis langdon (view profile)

Direct link to this comment:https://www.mathworks.com/matlabcentral/answers/444797-looping-through-3rd-dimension#comment_670955

## Matt J (view profile)

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