What is wrong with my code - Harris corner detector

Hi, when I am trying to implement the Harris corner detector, but when I run this code, all that is printing is a straight line. I don't know what the problem is.

function [y, r, c] = part2(threshold, sigma, radius)
im = 'einstein.jpg';
im = double(im);
e = 2.71828;
%threshold = 5*e - 4;
%sigma = 3;
%radius = 3;
k = 0.04;

%Definition of filters used to computer the image derivatives by utilizing
%the Sobel operator
dx = [-1 0 1; -2 0 2; -1 0 1];
dy = dx';

%Computation of image derivatives Ix and Iy using convolution
Ix = conv2(im, dx, 'same');
Iy = conv2(im, dy, 'same');

%Generation of Gaussian smoothing filter w(u,v)
w = fspecial('gaussian', 6*sigma, sigma);

%Computation of Ix2, Iy2, and Ixy
Ix2 = Ix.^2;
Iy2 = Iy.^2;
Ixy = Ix.*Iy;

%Computation of smoothed versions of Ix2, Iy2, and Ixy
Ix2smooth = conv2(Ix2, w, 'same');
Iy2smooth = conv2(Iy2, w, 'same');
Ixysmooth = conv2(Ixy, w, 'same');

%Computation of cornerness measure M
det = (Ix2smooth.*Iy2smooth) - Ixysmooth.^2;
trace =Ix2smooth + Iy2smooth;
y = det - k*(trace).^2;

%Performance of non-maximal suppression
suppress = ordfilt2(y, radius, threshold); 
[r, c] = find(y);

imshow(im);
plot(c, r);
%end

Answer 1

[Image Analyst]

Why not just use the built-in corner() function?