Plotting contours of a function

2020 6 18
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更新时间：2020 6 18
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Dear expert.
I am just a beginner when it comes to using MATLAB. Would anybody be so kind and show me the rope of this particular problem? I would like to use this as the base for my further practice.
Let z = f(x, y) = 2x y − y 2 − 4x 2 + 3y.
Draw the contour plot of the function. Point out the local extreme and the saddle point on that figure.
I would like to express my gratitude to your concern!

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madhan ravi
madhan ravi 2020-6-18
You need to show some effort. And by posting this question , you should be aware that your professor/teacher could find this thread easily as you do. So after the answerers spend time to answer your question don’t edit your question away by saying some lame reasons.
Kyle Dalminton
Kyle Dalminton 2020-6-18
I appreciate your advice and I am sorry if the way I posted my question gave you the wrong idea. I fully understood and would willingly accept any concequence when I decided to post this question. And also, disregarding the answerers' efforts by editing the question is something that I could never bring myself to do. If you do not have any trust in me, can you suggest anyway that I can do to earn it?
I was not informed about how to use MATLAB and my professor told me to learn from someone other than him. I tried Google but the results were too general. So my last resort was to ask somebody for an advice. I do not need a fully coded answer, all I asked was just a list of things I need to pay attention on. That is what called "the rope" I believe.
Finally, I am very sorry and hope you will forgive me for wasting your time and concern on such an ignorant person who had never touched MATLAB in his life.
I wish you a good day.
madhan ravi
madhan ravi 2020-6-18
编辑：madhan ravi 2020-6-18
Didn’t mean it personally, it was meant generally. Have a good day ;). Don’t be sorry because you didn’t do anything wrong.
Kyle Dalminton
Kyle Dalminton 2020-6-18
Okay, sorry if I went overboard up there :). Your advice has been noted. Thanks again :)

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KSSV
KSSV 2020-6-18

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  1. Fix the limits of x and y. Use linspace for this. Read about linspace.
  2. Make x, Y to a grid using meshgrid. Read about this.
  3. Write your formula i.e f(x,y) interms of matrices X, Y. Read about element by element operations.
  4. Now you got f as a matrix, now you can use contourf.
  5. To find the local extreme use min. Read about this function.
Read about MATLAB basics. https://www.tutorialspoint.com/matlab/index.htm

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Kyle Dalminton
Kyle Dalminton 2020-6-18
Much appreciated my good sir. I had been completely lost until I saw your answer. I will try to figure out the rest on my on.
I wish you a good day.

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