How to store output of a for loop in a matrix?

Hi guys,

I'm having difficulty storing my output values from a loop into a matrix. And whenever I try the solution mentioned in other examples the error preallocate comes up.

My code is below:

P= [10 20 30]

A=1230

B=0.14

Idir=0

for index = 1:3

Idir=(A/(exp(B/sin(P(index)))))

end

Answer 1

[madhan ravi]

Idir=zeros(size(P)); % this is how you preallocate before loop

Note: In this case you don’t need a loop.

[madhan ravi]

Inside loop:

Idir(index)=... % inside loop 
 %  ^^^^^^^-—-—- to store values

[Jamil Dudhwala]

How would i not need a loop?(sorry, I am quite new to coding)

[Stephen23]

"How would i not need a loop?"

https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

>> I = A./exp(B./sin(P))
I =
         1591       1055.1       1417.2    

https://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users

[Jamil Dudhwala]

Thank you, that worked.

But in that case, in MATLAB, when should for loops be used?

[madhan ravi]

Definitely I would suggest you to read the link suggested by stephen , once if you get familiarized with all the functions then you will know

When to use it ?

How to use it ?

Where to use it ?