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Organize data as vector matrix and do calculation ?

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Yu-Chen
Yu-Chen on 30 May 2013
I want to organize the data returned by sph2cart as a matrix with vector element and all the element in matrix will perform some calculation(vector-vector or vector-scalar calculation) with a vector. Here is an example i achieve this however it's somewhat redundant, how could i make it more terse ? Thanks.
lightV = zeros(1, 1, 3);
lightV(1,1,1) = 0.5;
lightV(1,1,2) = 0.4;
lightV(1,1,3) = 0.7;
[Az El] = meshgrid(0:60:360, 0:15:90);
[x y z] = sph2cart(Az*pi/180, El*pi/180, 1);
refV = zeros(size(Az,1), size(Az,2), 3);
radius = zeros(size(Az,1), size(Az,2));
for i = 1:size(Az,1)
for j = 1:size(Az,2)
refV(i,j,1) = -x(i,j);
refV(i,j,2) = -y(i,j);
refV(i,j,3) = z(i,j);
radius(i,j) = dot(refV(i,j,:), lightV(1,1,:));
end
end

Accepted Answer

Andrei Bobrov
Andrei Bobrov on 30 May 2013
Edited: Andrei Bobrov on 30 May 2013
[Az, El] = meshgrid(0:60:360, 0:15:90);
[x, y, z] = sph2cart(Az*pi/180, El*pi/180, 1);
refV2 = cat(3,-x,-y,z);
lightV = [.5 .4 .7];
radius = sum(bsxfun(@times,refV,reshape(lightV,1,1,[])),3);
or
radius = reshape([-x(:), -y(:), z(:)]*lightV.',size(x));

More Answers (2)

Iman Ansari
Iman Ansari on 30 May 2013
lightV = zeros(1, 1, 3);
lightV(1,1,1) = 0.5;
lightV(1,1,2) = 0.4;
lightV(1,1,3) = 0.7;
[Az El] = meshgrid(0:60:360, 0:15:90);
[x y z] = sph2cart(Az*pi/180, El*pi/180, 1);
refV=cat(3,-x,-y,z);
radius= lightV(1,1,1)*-x+lightV(1,1,2)*-y+lightV(1,1,3)*z

David Sanchez
David Sanchez on 30 May 2013
a couple of changes:
% you know the values from the start and no need of 3D matrix
lightV = [.5 .4 .7];
[Az El] = meshgrid(0:60:360, 0:15:90);
[x y z] = sph2cart(Az*pi/180, El*pi/180, 1);
refV = zeros(size(Az,1), size(Az,2), 3);
radius = zeros(size(Az,1), size(Az,2));
for i = 1:size(Az,1)
for j = 1:size(Az,2)
refV(i,j,1) = -x(i,j);
refV(i,j,2) = -y(i,j);
refV(i,j,3) = z(i,j);
ref = reshape(refV(i,j,:),1,3); % reshape to 2D matrix
radius(i,j) = dot(ref, lightV(1,:));
end
end

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