What is the correct way to use arrays with function inside for loop?

function [ z ] = z_funct( x,y )
     z=0.0817.*(3.71.*sqrt(x)-0.25.*x+5.81).*(y-91.4)+91.4;
end

x=[1 2 3 4 5];

y=[-20:2:40];

for i=1:5

      z(i)=z_funct(x(i),y);

end

z

What I actually want to do is to calculate z, when x vary, but y stays the same

This operation returns error: In an assignment A(I) = B, the number of elements in B and I must be the same.

I know it is something wrong with my array dimensions, but I can't figure it out.

Answer 1

[Matt Fig]

If you want to hold y as a vector, then for every x(i) in the loop your function call will return a vector. You cannot store a vector in a single numeric array element. Use a cell array instead:

z_funct = @(x,y) 0.0817*(3.71*sqrt(x)-0.25*x+5.81)*(y-91.4)+91.4

x=[1 2 3 4 5];

y=-20:2:40;

for ii=1:length(x)
   z{ii} = z_funct(x(ii),y);
end

Now z is a cell array.

z{1} has z_funct(1,-20:2:40)

z{2} has z_funct(2,-20:2:40)

z{3} has z_funct(3,-20:2:40)

etc.

.

.

.

.

You could also make an array with those values:

for ii=1:length(x)
   z2(ii,:) = z_funct(x(ii),y);
end

Now z2 is an array with row 1 being z_funt(1,-20:2:40).

Answer 2

[Nigel]

thank you! it worked out well! I have more questions to ask later though :)