2 variables symbolic function representation

Hello everyone!

I need to represent a two variables function.

From the following determinant

A =

I obtained the quadratic equation:

a =

These are the vectors p and q:

p00 = 0.909722222222223

p10 = -0.233216488601376

p01= 0.264523899711384

p20=-1.06968750000000

p11=-0.0207056503962889

p02=0.578645833333333

q00=0.907638888888890

q10=0.00799330706899891

q01=0.0257069830283098

q20=0.0382031250000013

q11=0.0414113007925775

q02=-0.628619791666669

I want to impose the function a ==0 and in order to obtain the curve and then I would like to represent it in a graph.

Is there a way to do it?

I used ht = matlabFunction(a) to obtain

ht = function_handle with value:

@(p01,p02,p10,p11,p20,q01,q10,q11,q20,x,y)(p20.*q11.*2.0-p11.*q20.*2.0).*x.^2+(p20.*q20.*4.0-p02.*q20.*4.0).*x.*y+(p10.*q11-p01.*q20.*2.0-p11.*q10+p20.*q01.*2.0).*x+(p11.*q20.*2.0-p02.*q11.*2.0).*y.^2+(p11.*q01-p02.*q10.*2.0-p01.*q11+p10.*q20.*2.0).*y+(p10.*q01-p01.*q10)

I don't understand if it is useful.

Thank you very much!

Laura

Answer 1

[VBBV]

Hi @laura bagnale, you can use the function handle and choose a suitable plot function for representation that best fits your needs

p00 = 0.909722222222223;
p10 = -0.233216488601376;
p01= 0.264523899711384;
p20=-1.06968750000000;
p11=-0.0207056503962889;
p02=0.578645833333333;
q00=0.907638888888890;
q10=0.00799330706899891;
q01=0.0257069830283098;
q20=0.0382031250000013;
q11=0.0414113007925775;
q02=-0.628619791666669;

%using function handle
a = @(x,y)(p20.*q11.*2.0-p11.*q20.*2.0).*x.^2+(p20.*q20.*4.0-p02.*q20.*4.0).*x.*y+(p10.*q11-p01.*q20.*2.0-p11.*q10+p20.*q01.*2.0).*x+(p11.*q20.*2.0-p02.*q11.*2.0).*y.^2+(p11.*q01-p02.*q10.*2.0-p01.*q11+p10.*q20.*2.0).*y+(p10.*q01-p01.*q10)

a = function_handle with value:
    @(x,y)(p20.*q11.*2.0-p11.*q20.*2.0).*x.^2+(p20.*q20.*4.0-p02.*q20.*4.0).*x.*y+(p10.*q11-p01.*q20.*2.0-p11.*q10+p20.*q01.*2.0).*x+(p11.*q20.*2.0-p02.*q11.*2.0).*y.^2+(p11.*q01-p02.*q10.*2.0-p01.*q11+p10.*q20.*2.0).*y+(p10.*q01-p01.*q10)

f = a([-5:5],[-5:5])  % give the range of values for x 

f = 1x11

-9.1020 -5.7296 -3.1340 -1.3152 -0.2733 -0.0081 -0.5198 -1.8082 -3.8735 -6.7156 -10.3345

<mw-icon class=""></mw-icon>

<mw-icon class=""></mw-icon>

% example 1
plot(f)

%example 2
[X,Y] = meshgrid(linspace(-5,5,50),linspace(-5,5,50));
surf(X,Y,a(X,Y))