Exclude point from my regression

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?

[KSSV]

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

[valerio auricchio]

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

Answer 1

[KSSV]

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 

[valerio auricchio]

I understand what you have write but i only want to remove from the vector r and c the coordinates of the pixel lower than a value

[KSSV]

[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 a be pixel values you want to remove 
idx = p < a ; 
r(idx) = []; c(idx) =[] ;   % remove those points which have pi pixel 

[valerio auricchio]

Whan i do Interp1 i recive the error "wrong number of input arguments" and i have converted I in double

[KSSV]

It should be interp2. My typo error. Now I have edited the answer. Also you can pick your required pixlels using find.

[valerio auricchio]

Still reciv error

I=imread('Immage.bmp')
ID=double(I);
[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 a be pixel values you want to remove 

idx = p < a ; 
r(idx) = []; c(idx) =[] ; 

[KSSV]

Attach your image.

[valerio auricchio]

this is the error message:

Error using griddedInterpolant

Sample values must be of type double or single.

Error in interp2>makegriddedinterp (line 228)

F = griddedInterpolant(varargin{:});

Error in interp2 (line 136)

F = makegriddedinterp(X, Y, V, method,extrap);

[valerio auricchio]

this is the immage

[KSSV]

[r, c] = find(I>=224 & I<=225) ;

If you see (r,c) they are empty. There is no value in I which is greater than 211.

For demo purpose, you can check the below code:

I=imread('Image.bmp') ;
ID=double(I);
[m,n] = size(I) ; 
[X,Y] = meshgrid(1:n,1:m) ; 

[r, c] = find(I>=150 & I<=180) ;
% Get the pixel values at r, c 

p = interp2(X,Y,ID,r,c) ;  % if it throws error comvert I into double 
% Let a be pixel values you want to remove 
a = 170 ; 

idx = p < a ; 
r(idx) = []; c(idx) =[] ; 

[valerio auricchio]

Yes it was my error but with the right range i stil have the same error

[KSSV]

What range you have given?

[valerio auricchio]

range 170 180

[KSSV]

I am not getting any error....the given code is working fine.