I have a problem with surface parameters (fsurf)

Hello there, this is my first time using this site for help so if i don't get the etiquette right please do let me know. OK so i am trying to plot the following surface f(x,y)= (3*x^2+y^2)*exp(-x-y) with intervals -2 < x < 2 and -2 < y < 2 i have produced the following code:

syms x y
f(x,y) = (3*x^2+y^2)*exp(-y-x);
fsurf(f,[-2 2 -2 2])

However the results are terrible i have tried changing the parameters and tried using a mesh but i get nowhere. Now i have been using a tool online called Calcplot3D see here https://www.monroecc.edu/faculty/paulseeburger/calcnsf/CalcPlot3D/ this tool displays the function how i would expect it to look, i don't understand why i can't replicate this in matlab.

Any help would be brilliant Best Regards Jake

Answer 1

[madhan ravi]

syms x y %edited
f(x,y) = (3*x^2+y^2)*exp(-y-x);
ezsurf(f)
xlim([-2 2])
ylim([-2 2])
zlim([-5 5])

[madhan ravi]

 "_i don't understand why i can't replicate this in matlab._“

If you use symbolic parameters make sure to use ezsurf()

[Jake Simmonds]

Thank you, the following code with my function still produces unexpected results, the function looks nothing like that :(

[madhan ravi]

Check edited answer

[Jake Simmonds]

I have checked the function if you run the code you get a plot that looks like sheet of paper that looks like it has been lifted at one corner. However if you use that webtool for the function f(x,y)= (3*x^2+y^2)*exp(-x-y) you get the proper function!

[madhan ravi]

No not at all matlab is sophisticated than you think there are two figures in my code plus the one which you suggested in the website has a different equation look carefully!!

[Jake Simmonds]

I guess i haven't made myself clear enough, what i meant to say is that using that tool to evaluate the function i was looking at (3*x^2+y^2)*exp(-x-y) you get a much more expected "normal" plot.

[madhan ravi]

Could you upload the picture of your expected plot ?

[Jake Simmonds]

[madhan ravi]

zlim([-5 5])

[madhan ravi]

In fact it’s the same plot but the scaling was different that’s why the figure seemed to be different add the previous comment as your last line and see the difference

[madhan ravi]

See the edited answer now

[Jake Simmonds]

Ah ok, it's still not as nice though is it as the plot above? it's an improvement though so thanks. I think i will stick to that web-tool though.

[madhan ravi]

If you get used to Matlab you may find it easy to manipulate anyways glad that you got the answer for your question , make sure to accept the answer so that people know that question is solved

Answer 2

[Matt J]

f = @(x,y) (3*x.^2+y.^2).*exp(-y-x);
fsurf(f,[-2 2 -2 2])

[Jake Simmonds]

Should it not have the dot before *exp ? like so: f = @(x,y) (3*x.^2+y.^2).*exp(-y-x); Also this still does not replicate the function as it should be!!!

[Matt J]

Yes, I have added .*