Rotating and shifting a meshgrid

Hello,

I have a 257x257 X,Y coordinate meshgrid that I need to rotate by 10 degrees (counterclockwise) and then move it along the x and y axis by adding a certain number to it (175.5362) in order to move it to the right location. This is what I have so far:

%Create the meshgrid
Xinit = 0:3125:800000;
Yinit = 0:3125:800000;
[Xq,Yq] = meshgrid(Xinit,Yinit);

When doing it in vector arrays I would do this:

theta=-10; %TO ROTATE CLOCKWISE BY X DEGREES
R=[cosd(theta) -sind(theta); sind(theta) cosd(theta)]; %CREATE THE MATRIX
rotXY=XY*R'; %MULTIPLY VECTORS BY THE ROT MATRIX

But this is a 257x257 matrix and I get this subsequently:

"Error using *

Inner matrix dimensions must agree."

I assume the second part of my question is just a matter of doing this:

%SHIFTING
Xq=Xq+175.5362;
Yq=Yq+175.5362;

Apologies if this is something very simple that I am missing again,

Thank you,

Pavlos

Answer 1

[Star Strider]

One approach:

%Create the meshgrid
Xinit = 0:3125:800000;
Yinit = 0:3125:800000;
[Xq,Yq] = meshgrid(Xinit,Yinit);
Z = sin(Xq/40000) .* cos(Yq/40000);                     % ‘Z’ To Provide A Surface

figure
mesh(Xq,Yq,Z)                                           % Original
grid on

XY = [Xq(:) Yq(:)];                                     % Create Matrix Of Vectors
theta=-10; %TO ROTATE CLOCKWISE BY X DEGREES
R=[cosd(theta) -sind(theta); sind(theta) cosd(theta)]; %CREATE THE MATRIX
rotXY=XY*R'; %MULTIPLY VECTORS BY THE ROT MATRIX 

Xqr = reshape(rotXY(:,1), size(Xq,1), []);
Yqr = reshape(rotXY(:,2), size(Yq,1), []);
%SHIFTING
Xqrs = Xqr+175.5362;
Yqrs = Yqr+175.5362;

figure
mesh(Xqrs, Yqrs, Z)                                     % Rotated & Shifted
grid on

See if that gives you the result you want.

[Pavlos Farangitakis]

Hi,

It works absolutely fine! Thank you so much!

Pavlos

[Star Strider]

As always, my pleasure!

[Scott Smith]

This was very helpful! I was trying to follow what imrotate does to the x and y positions of an image that has x and y coordinate data (after upscaling the image), your answer was invaluble! Thank you!

[Star Strider]

@Scott Smith — My pleasure!

Answer 2

[Matt J]

 
 theta=-10;
 shift=[1,1]*175.5362;
 R=[cosd(theta) -sind(theta); sind(theta) cosd(theta)];
 
 
 szx=size(Xq);
 
 XY=reshape( [Xq(:)*Yq(:)]*R.' + shift  ,[sz,2]);
 
 Xq=XY(:,:,1);
 Yq=XY(:,:,2);