Any idea on how to create a n by n square matrix.

The size of the matrix follows the npanels=3

Let say for this case it is a 3 by 3 square matrix but if i want to create a 7 by 7 square matrix or a 15 by 15 square matrix I will have to repeat the procedure many times. I want MATLAB to be able to auto create a n by n square matrix by only changing the value of npanels.

Vector P,Vector x and Vector y are row vectors with 3 elements which is the value of npanels=3.

 npanels=3; %number of panels
  dP=2.4/npanels; %equal length panels
  P=[-1.2+(2.4/npanels)/2:dP:1.2-(2.4/npanels)/2]; %panels x-ccordinates
  a=1.25; %major axis
  b=0.75; %minor axis
  O=[pi-pi/(2*npanels):-pi/(npanels):pi/(2*npanels)]; %boundary points
  r=(a*b)./sqrt((b*cos(O)).^2+(a*sin(O)).^2); % ellipse in polar coordinates
  x=r.*cos(O); %x-coordinate
  y=r.*sin(O); %y-coordinate

C1j=(y(1).*dP)./((x(1)-P).^2+(y(1).^2));
C2j=(y(2).*dP)./((x(2)-P).^2+(y(2).^2));
C3j=(y(3).*dP)./((x(3)-P).^2+(y(3).^2));

C=[C1j;C2j;C3j]

Answer 1

[Paulo Silva]

v=1:npanels;
C=reshape(cell2mat(arrayfun(@(v)(y(v).*dP)./((x(v)-P).^2+(y(v).^2)),...
v,'uni',false)),npanels,npanels)';

[Paulo Silva]

Andrew code is much much faster and clean, use his code!

[Andrew Newell]

You're very kind!

Answer 2

[Andrew Newell]

Use meshgrid:

npanels=3; %number of panels
dP=2.4/npanels; %equal length panels
P=[-1.2+(2.4/npanels)/2:dP:1.2-(2.4/npanels)/2]; %panels x-ccordinates
a=1.25; %major axis
b=0.75; %minor axis
O=[pi-pi/(2*npanels):-pi/(npanels):pi/(2*npanels)]; %boundary points
[P,O] = meshgrid(P,O);
r=(a*b)./sqrt((b*cos(O)).^2+(a*sin(O)).^2); % ellipse in polar coordinates
x=r.*cos(O); %x-coordinate
y=r.*sin(O); %y-coordinate
C = y*dP./((x-P).^2 + y.^2)

[Paulo Silva]

good code +1 vote

Answer 3

[Yoon Hong Ng]

Thank you Mr. Newell and Mr.Silva.