problem with polyfit function

Question

mounim 2012-12-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/56558-problem-with-polyfit-function

hey everyone, i ahope someone can help me with this code, what i am trying to do is plotting a fitting line. my graf is shown, but the fit line, is not where it should be, it is the wrong direction, and the wrong angle, please what i am doing wrong ?

this is my code :

for k=50:100
     oneRow = binaryImage(k, :);
     leftEdge = find(oneRow, 1, 'first');
     rightEdge = find(oneRow, 1, 'last');
     hold on;
     midpoints(k) = (leftEdge + rightEdge)/2;
     %plot the left and right edge
     plot(leftEdge, k, 'rx','LineWidth',2);
     plot(rightEdge, k, 'rx','LineWidth',2);
     % CENTER POINTS 
     plot(midpoints(k), k, 'yx','LineWidth',2);
end
X=[1:100];
new_x = linspace(1, 100);
coeffs = polyfit(X, midpoints, 1);
new_y = polyval(coeffs, new_x);
plot(new_x,new_y, '-','LineWidth',2);