How to plot a point 300 pixels to the right in an image?

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Sean 2015-2-23

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编辑： Sean 2015-2-23

So I've a variable created called 'J' which is situated at a certain point in the image, how do I plot it 300 pixels to the right of the point its situated? it seems to be moving along the wrong axis when Im trying to move it rightwards.

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Image Analyst 2015-2-23

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在 MATLAB Online 中打开

What is J? I'll assume it's a 1 by 2 array with the x (column) coordinate, followed by the y (row) coordinate. Then to plot 300 columns to the right, do

plot(J(1)+300, J(2), 'r*', 'MarkerSize', 20, 'LineWidth', 2);

Make sure you're not making the very common mistake of mixing up x,y with row, column - that's almost certainly what you're doing. Remember images take indexes of (row, column) which is (y, x) while plot() takes (x,y) which is (column, row). Make sure you get it straight - like I said, this is a very common error.

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Sean 2015-2-23

编辑：Sean 2015-2-23

在 MATLAB Online 中打开

I've used the command

J=mean(fit);

to create the midpoint for the blue line, however when I go to plot it, it is situated at the very beginning of the blue line, therefore I was trying to move 'J' to the very centre of the picture by adding 512 to it. Is there a better way to create the midpoint for the blue line (sfit)? since I don't know its x coorrdinate ?

Sean 2015-2-23