looping for a function

Hi, can I apply

[output1, output2] = calculate(b);

in a 3D data such as 80x30x400 data?

[KSSV]

It depends on your function calculate.

[Nurul Ain Basirah Zakaria]

is it arrayfun?

Answer 1

[KSSV]

This is what you are looking for?

[m,n,p] = size(b) ;   % b is matrix of size 80x30x400
iwant = zeros(p,2); 
for i = 1:p
    [output1, output2] = calculate(b(:,:,i));
    iwant(i,:) = [output1, output2] ;
end

[Nurul Ain Basirah Zakaria]

i tried something like this,

for i=1:84
for j=1:36
    [freq, duration]=drought(data(i,j,:));
end
end

but i get

Output argument "duration" (and maybe others) not assigned during call to "drought"

now i am reading this: https://www.mathworks.com/matlabcentral/answers/97825-why-do-i-get-the-error-output-argument-variable-and-maybe-others-not-assigned-during-call-t

[KSSV]

What is drought? There is no function or variable on this name, so the error.

[Nurul Ain Basirah Zakaria]

drought is my function

[KSSV]

That case function is not present in the folder you are working. Keep the function in the pwd or add path of the function.

[Nurul Ain Basirah Zakaria]

but i already add to path, when i run it for a single data or vector, it works fine. But, in order to run it in 3D (84x36x400) data, it comes out as:

for i=1:84
for j=1:36
[freq, duration, peak, severity]=drought(3D(i,j,:));
end
end

Output argument "duration" (and maybe others) not assigned during call to "drought".

[KSSV]

There is no output called duration in drought.

Answer 2

[Walter Roberson]

This has nothing to do with a missing function.

Your code in drought.m is defined to expect at least four output variables -- otherwise you would have received an error about too many output arguments before you reached the error you did.

Your code in drought.m assigns some value to the first of the output variables it assigns.

However, your code in drought.m does not assign any value to the second of the output variables it assigns.

At the moment we do not have enough information to know whether drought.m never assigns to the second output variable, or if instead it does not assign to the second output variable under some conditions and the conditions happen to be such that it does not assign.

For example,

function [A, B, C] = drought(data)
   if any(data(:) < 0    %negative rainfall ??
       A = nan;     %signal invalid data
       return
   end
   A = mean(data);
   B = std(data);
   c = var(data);
end

In this example code, B is not assigned to if there are any negative values in the input, and C is never assigned to under any conditions. In this example code it could well be the case that the intention was to assign to C instead of c, but MATLAB doesn't know anything about intentions.

[Nurul Ain Basirah Zakaria]

but if i apply it for single data, i got the outcomes, but this problem appeared when i try to calculate for 3D data.

[Walter Roberson]

We have not seen your function drought so it is difficut to say why it is failing.

Could you confirm that it is failing when the input is a 1 x 1 x Something array (such as 1 x 1 x 400) ?