MATLAB: Do the coeffvalues not produce a sensible result

coeffvaluesMATLAB

I have a script that uses the fit fuction on some data using a poly55 fit type. I then use this to get the coeffvalues for the fittted curve and try to replot the surface using the coeffvalues but the result produced is orders of magnitude different from the original data.

Script attached as well as some example data.

Can anyone explain what is happening or recommend a way forward?

Best Answer

If you use the 'Normalize','on' fitting option, your polynomial has powers of (x-meanx)/stdx and (y-meany)/stdy instead of x and y.

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MATLAB: How to speedup mean and std calculation on GPU

To calculate the standard deviation, the mean must be calculated again. Try to combine this:

x2     = g_p(d-w+q-1:d+q-2,:);
mean_x = sum(x2, 1) / w;
xc     = x2 - mean_x;                % Auto-expand: >= R2016b
% xc   = bsxfun(@minus, x2, mean_x);
std_x  = vecnorm(xc) / sqrt(s - 1);  % vecnorm: >= R2017b
% std_x  = sqrt(sum(xc .* xc, 1)) / sqrt(s - 1);

for the mean only the first and the last element changed between the iterations. Use this detail:

mean_x = sum(g_p(d-w:d-1, :) / w;  % For q=1
for q = 1:n1-d
   ...
   mean_x = mean_x - (g_p(d-w+q-1, :) + g_p(d+q-1, :)) / w;
end

MATLAB: How to declare a specified row in an image as a variable

You mean like this:

[rows, columns] = size(AR);
y1 = 200
y2 = 315
row1 = AR(y1, :); % Extract this line of gray levels from the image.
row2 = AR(y2, :);
plot([0, columns], [y1, y1], 'g'); 
plot([0, columns], [y2, y2], 'b');
meanX1 = mean(row1);
stdX1 = std(double(row1));
meanX2 = mean(row2);
stdX2 = std(double(row2));

Best Answer

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MATLAB: How to speedup mean and std calculation on GPU

MATLAB: How to declare a specified row in an image as a variable

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