Detection of line segments and length

I am trying to have MATLAB detect multiple line segments in a images and then tell the length (in pixels). I have tried the following code:

    I=imread('GFP1C2.tif');
canny=edge(I,'canny');
[H,T,R]=hough(canny);
imshow(H,[],'XData',T,'YData',R,'InitialMagnification','fit')
xlabel('\theta'),ylabel('\rho')
axis on, axis normal, hold on
P=houghpeaks (H,5,'threshold',ceil(0.8*max(H(:))));
x=T(P(:,2));y=R(P(:,1));
plot(x,y,'s','color','white');
lines=houghlines(BW,T,R,P,'FillGap',5,'MinLength',7);
figure,imshow(canny),hold on
max_len=0;
for k=1:length(lines)
    xy=[lines(k).point1;lines(k).point2];
    plot(xy(:,1),xy(:,2),'Linewidth',2,'Color','green');
    plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
    plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');
    len=norm(lines(k).point1-lines(k).point2);
    if (len>max_len)
        max_len=len;
        xy_long=xy;
    end
end

This code will neither accurately detect the line segments nor will tell me the length of the segment. Help is appreciated; thanks!