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plot3 out of loop

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Oday Shahadh
Oday Shahadh on 9 Jun 2020
Commented: Oday Shahadh on 10 Jun 2020
Can you please fix empty plot in below script
clear
close all
format long
theta=0:10:360;
rho=0:.5:2;
L=-2:0.5:2;
X= cell(3,1) ; Y= cell(3,1);Z = cell(3,1) ;
for i=1:length(L)
for j=1:length(rho);
for k=1:length(theta);
[x,y,z]=pol2cart(theta(k),rho(j),L(i));
X{i} = x ; Y{i} = y ; Z{i} = z ;
end
end
end
figure(1)
hold on
plot3(X,Y,Z)

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Accepted Answer

David Hill
David Hill on 9 Jun 2020
clear;
theta=0:10:360;
rho=0:.5:2;
L=-2:0.5:2;
[a,b,c]=meshgrid(theta,rho,L);
[x,y,z]=pol2cart(a,b,c);
plot3(x(:),y(:),z(:));

  3 Comments

Oday Shahadh
Oday Shahadh on 10 Jun 2020
hi David,
what does x(:), means?
David Hill
David Hill on 10 Jun 2020
It just converts x matrix into a column vector (reshaping to 1 dimension)
Oday Shahadh
Oday Shahadh on 10 Jun 2020
Very good job David
Can I ask another thing pls?

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More Answers (1)

Adam Danz
Adam Danz on 9 Jun 2020
A critical missing bit of information is missing from your questions. An error is thrown by the last line in your quesiton.
Error using plot3
Not enough input arguments.
This is because your plot3() inputs are cell arrays. It looks like your loops produce scalar values on each iteration so those values can be stored within a numeric array which will be much easier to use.
Your loops were overwriting the x,y,z values on each iteration of the j and k loops. The method below will store those values but it's up to you to make sure this makes sense in the context of whatever you're doing.
theta=0:10:360;
rho=0:.5:2;
L=-2:0.5:2;
% Numeric arrays, not cell arrays
% Also, preallocation to the correct size
X = nan(length(L), length(rho), length(theta)) ;
Y = X;
Z = X;
for i=1:length(L)
for j=1:length(rho)
for k=1:length(theta)
[x,y,z]=pol2cart(theta(k),rho(j),L(i));
X(i,j,k) = x ; Y(i,j,k) = y ; Z(i,j,k) = z ; % Store all of the value
end
end
end
As for plotting, it's not clear how you would like to use these values. plot3() creates a 2D plot but the inputs cannot have more than 2 dimensions and the x y z values above have 3 dimensions.

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