# How to convert the points with respect to co-ordinate system?

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Swapnil Rane on 30 Mar 2018
Commented: Walter Roberson on 30 Mar 2018
I have huge three 90*85 matrices with x,y,z values calculated from the left upper corner of the matrix. I would like to change the points with respect to new coordinate system.
How can I convert the points? Do you need more explanation?
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Swapnil Rane on 30 Mar 2018
I have imported a image to find the pixel values. As per my knowledge the location of (0,0) of the matrix in the left upper corner. But the local coordinate system is at the centre of the body. How can I create a transformation matrix? to convert all the points according to the new coordinate system Walter Roberson on 30 Mar 2018
Usually you would create a transformation matrix, either 3 x 3 or 4 x 4, and you would take the three matrices and reshape them and concatenate them to create columns of a vector, and then use matrix multiplication by the transformation matrix. Take the N x 3 or N x 4 matrix that results and reshape the columns back to the original size of your input matrices.
Walter Roberson on 30 Mar 2018
Just subtract off the location of the center from the coordinates.
x_center = mean(x(:));
y_center = mean(y(:));
z_center = mean(z(:));
newx = x - x_center;
newy = y - y_center;
newz = z - z_center;

Abhishek Ballaney on 30 Mar 2018
https://in.mathworks.com/help/matlab/cartesian-coordinate-system-conversion.html
Swapnil Rane on 30 Mar 2018
I just want to transform the coordinate system and get the location of points according to new coordinate system