# pol2cart in loop and pre-allocating

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Oday Shahadh on 9 Jun 2020
Commented: Oday Shahadh on 9 Jun 2020
hi all,
how can I put [x,y,z]=pol2cart(theta,rho,z), in tripple loop for different values of heta,rho,z, as well how to pre allocate [x,y,z]?
Regards

KSSV on 9 Jun 2020
You need not preallocate (x,y,z) when you use the function.....If you want to run it thrice, you can do the following.
X = cell(3,1) ; Y = cell(3,1);Z = cell(3,1) ;
for i = 1:3
[x,y,z]=pol2cart(theta{i},rho{i},z{i}) ;
X{i} = x ; Y{i} = y ; Z{i} = z ;
end
If all the size of theta, rho, z are same. You can use matrices instead of cells.
N = length(theta) ;
X = zeros(N,3) ; Y = zeros(N,3); Z = zeros(N,3) ;
for i = 1:3
[x,y,z]=pol2cart(theta(:,i),rho(:,i),z(:,i)) ;
X(:,i) = x ; Y(:,i) = y ; Z(:,i) = z ;
end
Oday Shahadh on 9 Jun 2020
yes there is a values ,it works just in case that insert plot command inside the loop with ('.')
I need to put the plot outside,pls
thanks

David Hill on 9 Jun 2020
No need for loop or for preallocating when you just execute for arrays of theta,rho, and Z.
theta=linspace(0,pi,100);
rho=linspace(0,10,100);
Z = linspace(10,100,100);
[x,y,z]=pol2cart(theta,rho,Z);