how to plot quadratic equation with 2 variable

f(x,y)= 1/2*x^2 + x*y + y^2 + y

i tried plotting using Fimplicit function but i am getting some error. copied below

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>> fimplicit3(@(x,y) 1/2*x.^2+ x*y+ y.^2+y)

Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to

return an output with the same size and shape as the input arguments.

> In matlab.graphics.function.ImplicitFunctionSurface>getFunction

In matlab.graphics.function.ImplicitFunctionSurface/updateFunction

In matlab.graphics.function.ImplicitFunctionSurface/set.Function

In matlab.graphics.function.ImplicitFunctionSurface

In fimplicit3>singleFimplicit (line 184)

In fimplicit3>@(f)singleFimplicit(cax,f,limits,extraOpts,args) (line 146)

In fimplicit3>vectorizeFimplicit (line 146)

In fimplicit3 (line 120)

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Also ince this is quadratic equation i was expecting a concave or convex figure but i am getting a cylindrical image.

can anyone explain...??

Answer 1

[Ameer Hamza]

You need to use fsurf() and use element-wise operators in your function handle

fsurf(@(x, y) 1./2*x.^2+ x.*y+ y.^2+y)

Answer 2

[KSSV]

x = linspace(0,1) ;
y = linspace(0,1) ;
[X,Y] = meshgrid(x,y) ; 

f =  1/2*X.^2 +  X.*Y + Y.^2 + Y ;

surf(X,Y,f)