What is this error about?

Hi

I am trying to use an active contour and I get the error

Error using contour (line 46)
Input arguments for contour must be real. Use the function REAL to get the real part of the inputs.
Error in ruller (line 184)
        hold on,[c,h] = contour(phi,[0 0],'r','linewidth',1); hold off 

Can someone please explain me what this error is all about?

[Guillaume]

The error message seems clear. Some elements of phi are complex. contour (nothing to do with active contour) only work on real inputs, not complex

[KSSV]

[c,h] = contour(real(phi),[0 0],'r','linewidth',1);

[Stelios Fanourakis]

It is something wrong going on. The specific code, never had issue. Since, I integrated to an another code I get errors, such as the forementioned, where I shouldn't.

Althought, with KSSV suggestion I made the contour work, still it is not satisfactory working.

I attach two images.

How it used to work previously, where it was running autonomously and the error.jpg, that indicates how it is running now, which is not the way I want.

What's wrong with it?

[Stelios Fanourakis]

I use that code

 us = {'Iterations:','Time Step:', 'Kernel Size (sigma):', 'Data Term Weight'};
      
      t = cell2mat(us);
      e = str2num(t);
      
      numberOfLines = 4;
      dialogTitle = 'Specify optimization parameters for LGD';
      def = {'300', '0.1', '5', '20'};
      
      U = inputdlg(us,dialogTitle,numberOfLines,def); 
      
      i = cellfun(@str2num,U);
     r = real(i);
      
 Img = double(J(:,:,1));
 
      
NumIter = r(1); %iterations
timestep= 0.1; %time step
mu=0.1/timestep;% level set regularization term, please refer to "Chunming Li and et al. Level Set Evolution Without Re-initialization: A New Variational Formulation, CVPR 2005"
sigma = r(2);%size of kernel
epsilon = 1;
c0 = 2; % the constant value 
lambda1=1.05;%outer weight, please refer to "Chunming Li and et al,  Minimization of Region-Scalable Fitting Energy for Image Segmentation, IEEE Trans. Image Processing, vol. 17 (10), pp. 1940-1949, 2008"
lambda2=1.0;%inner weight
%if lambda1>lambda2; tend to inflate
%if lambda1<lambda2; tend to deflate
nu = 0.001*255*255;%length term
alf = r(4);%data term weight

[Jan]

This is a strange code. Why do you convert the cell string us to a matrix at first and try to convert it into a number by str2num? What do you expect as number output for the char vector 'Iterations:'? I assume, that:

      t = cell2mat(us);
      e = str2num(t);

is orphaned and should be deleted.

What is J ? The rest of the code does not contain the failing call to contour, so what is the relation to the question?