Exclude point from my regression

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valerio auricchio 2020-11-5

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关闭： MATLAB Answer Bot 2021-8-20

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Hi I'm doing regression with this code

I=imread('Immage.bmp')
%find the min and max
minimo= min(I(:))
massimo=max(I(:))
[r, c] = find(I>=224 & I<=225)
coefficients = polyfit(r, c, 1);
%xFit = x; % Option 1 : same number of points as the training set.
xFit = linspace(min(r), max(r), 2000); % Option 2 : lots of points, and not just where the training points are.
yFit = polyval(coefficients, xFit);
imshow(I)
hold on
plot(r, c, 'r*', 'LineWidth', 2, 'Markersize', 6)
hold on;
plot(xFit, yFit, 'm-', 'LineWidth', 5)
hold on;
line([1,2448],[1024,1024]);

'r' and 'c' are two vector thaht rappresent the coordinates (X,Y) of the pixel. I want to remove the pixel where the intensity is lower than a parameter. How can i do that?

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KSSV 2020-11-5

You cannot remove that pixle.......but you can replace that with some other value.

valerio auricchio 2020-11-5

I do not want to remove pixel i want to exclude them form the regression

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KSSV 2020-11-5

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https://ww2.mathworks.cn/matlabcentral/answers/637540-exclude-point-from-my-regression#answer_535510

编辑：KSSV 2020-11-5

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Let I be your m*n image.

[m,n] = size(I) ; 
[X,Y] = meshgrid(1:n,1:m) ; 
[r, c] = find(I>=224 & I<=225) ;
% Get the pixel values at r, c 
p = interp2(X,Y,I,r,c) ;  % if it throws error comvert I into double 
% Let pi be pixel values you want to remove 
idx = p == pi ;  % idx = abs(p-pi)<=10^-3  
r(idx) = []; c(idx) =[] ;   % remove those points which have pi pixel 