convert formula into coding form

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Syakira Akmal 2017-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/334913-convert-formula-into-coding-form

评论： PPO POT 2019-9-11

Hi, i have this kind of formula

 dy=(X,Y+1)-(X,Y-1)
 dx=(X+1,Y)-(X-1,Y)
 (X,Y)=(dx^2+dy^2)^1/2

and i want to convert into coding form.Can anyone help me? and I just get confuse whether the formula need to be to a second derivation or just power of 2 the value?

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Syakira Akmal 2017-4-11

在 MATLAB Online 中打开

correction for the formula

alpha(X,Y)=(dx^2_dy^2)^1/2

Rik 2017-4-11

What do you actually mean with this syntax? (And I would advise using sqrt instead of ^(1/2).)

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Answer 1

Image Analyst 2017-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/334913-convert-formula-into-coding-form#answer_262687

在 MATLAB Online 中打开

Use imgradient():

[Gx, Gy] = imgradientxy(I); % Gx is what you call dx and Gy is what you call dy.
[Gmag, Gdir] = imgradient(Gx, Gy); % Gmag is what you call alpha.

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Image Analyst 2019-8-25

Each point has exactly one gradient, with both a magnitude and a direction, which you can decompose into two orthogonal vectors along the x and y direction if you want or need to.

What is the average you desire being taken over? Gmag is the gradient magnitude at each point, like I said, so if you want the "average" gradient then you must want it averaged over several points. So . . . which points? All points in a square window centered at the point? If so, what is the window size? All points in a circular window centered around the point? Again, what size?

Possibly more important than that is WHY you want the average gradient. So, why do you want the average instead of the actual gradient?

PPO POT 2019-9-11