Why function gradmag isn´t working for me?

Dear all,

I have this code:

%addpath('/Applications/MATLAB_R2015b.app/toolbox/dip/common/dipimage')
% dip_initialise
%dipsetpref('imagefilepath','/Applications/MATLAB_R2015b.app/toolbox/dip/images')
%addpath /Applications/MATLAB_R2015b.app/toolbox/dip/common/dipimage/demos

img1 = imread('2_ct_bw150.png');
img = rgb2gray(img1);

x = 350+350*cos(0:0.1:2*pi)';
y = 350+350*sin(0:0.1:2*pi)';

imshow(img1);
hold on
plot([x;x(1)],[y;y(1)],'g')

alpha = 0.001;
beta = 0.9;
gamma = 100;
iterations = 50;

N = length(x);
a = gamma*(2*alpha+6*beta)+1;
b = gamma*(-alpha-4*beta);
c = gamma*beta;
P = diag(repmat(a,1,N));
P = P + diag(repmat(b,1,N-1), 1) + diag(   b, -N+1);
P = P + diag(repmat(b,1,N-1),-1) + diag(   b,  N-1);
P = P + diag(repmat(c,1,N-2), 2) + diag([c,c],-N+2);
P = P + diag(repmat(c,1,N-2),-2) + diag([c,c], N-2);
P = inv(P);

f = gradient(gradmag(img,30));

for ii = 1:iterations
   % Calculate external force
   coords = [x,y];
   fex = get_subpixel(f{1},coords,'linear');
   fey = get_subpixel(f{2},coords,'linear');
   % Move control points
   x = P*(x+gamma*fex);
   y = P*(y+gamma*fey);
   if mod(ii,5)==0
       plot([x;x(1)],[y;y(1)],'b')
   end
end
plot([x;x(1)],[y;y(1)],'r')

hold off

for segmentation, but this error appears:

Undefined function or variable 'gradmag'.

Error in ct_snakes (line 32)
f = gradient(gradmag(img,30));

Can you advise me, where is mistake? Thank you for your answers.

Answer 1

[Richard Zappulla]

gradmag is not standard MATLAB function. If downloaded it from the file exchange or GITHUB, make sure the folder in which it resides is on your path. Chances are, this is the issue causing the error you listed.

For convenience, here is the link to the MATLAB page describing how to add a folder to your path.

Answer 2

[Cris Luengo]

This code, which you have copied from my blog, requires DIPimage to run. Get it here: http://www.diplib.org/. Make sure you read the installation instructions.