Implicit function 2D plot

I am trying to plot a function of the form

y=f(x,y)

That is y as a function of x. Any help?

Thanks

Answer 1

[madhan ravi]

see fimplicit(), fplot() and ezplot()

fimplicit(@(x,y) x.^2 - y.^2 - 1)

fplot(@(x) sin(x)) 

syms x y
f(x, y) = sin(x + y)*sin(x*y);
ezplot(f)

[T S Singh]

@madhan I am using 2015 version so 'fimplicit' is not available. Can you please suggest me any other way.

[madhan ravi]

Use ezplot , if it doesn’t work either upload your function here

[T S Singh]

om = 4.0264e+05;
sd=.3*om;
k3=0.01;
ld=0.085;
c0=@(a)-(om^2+(3/4)*k3*a^2)*sd^2+(om^2+(3/4)*k3*a^2)*(om^2+(3/4)*k3*a^2+ld^2+2*y*ld+(3/2)*k3*a^2);
c1=@(a)2*(om^2+(3/4)*k3*a^2)*(2*y+ld)+2*y*(ld^2+2*y*ld+(3/2)*k3*a^2);
c2=@(a)2*(om^2+(3/4)*k3*a^2)+(3/2)*k3*a^2+ld^2+4*y^2+6*y*ld;
c3=2*(2*y+ld);
b1=@(dm)-2*dm*om*(y+ld);
b2=@(a,dm)(om^2+(3/4)*k3*a^2)+(3/2)*k3*a^2+ld^2+2*y*ld-(dm*om)^2;
eq=@(a,dm)sqrt((b1(dm)^2+b2(a,dm)^2)/(((dm*om)^4-c2(a)*(dm*om)^2+c0(a))^2+(c3*(dm*om)^3-c1(a)*dm*om)^2))-a;

I want to plot 'a vs dm' for dm=[0,3]

Thanks

[madhan ravi]

a and dm are arguments not equations be specific with clear explanation

[T S Singh]

eq=@(a,dm)sqrt((b1(dm)^2+b2(a,dm)^2)/(((dm*om)^4-c2(a)*(dm*om)^2+c0(a))^2+(c3*(dm*om)^3-c1(a)*dm*om)^2));
a=eq(a,dm);

I suppose the last expression is of the form

y=f(x,y)

Thanks

[madhan ravi]

om = 4.0264e+05;
sd=.3.*om;
k3=0.01;
ld=0.085;
c0=@(a)-(om.^2+(3./4).*k3.*a.^2).*sd.^2+(om.^2+(3./4).*k3.*a.^2).*(om.^2+(3./4).*k3.*a.^2+ld.^2+2.*y.*ld+(3./2).*k3.*a.^2);
c1=@(a)2.*(om.^2+(3./4).*k3.*a.^2).*(2.*y+ld)+2.*y.*(ld.^2+2.*y.*ld+(3./2).*k3.*a.^2);
c2=@(a)2.*(om.^2+(3./4).*k3.*a.^2)+(3./2).*k3.*a.^2+ld.^2+4.*y.^2+6.*y.*ld;
c3=2.*(2.*y+ld);
b1=@(dm)-2.*dm.*om.*(y+ld);
b2=@(a,dm)(om.^2+(3./4).*k3.*a.^2)+(3./2).*k3.*a.^2+ld.^2+2.*y.*ld-(dm.*om).^2;
eq=@(a,dm)sqrt((b1(dm).^2+b2(a,dm).^2)./(((dm.*om).^4-c2(a).*(dm.*om).^2+c0(a)).^2+(c3.*(dm.*om).^3-c1(a).*dm.*om).^2))-a;
a=linspace(1,3,1000); %fake data
m=linspace(0,3,1000);
plot(eq(a,m))

whats y value?

[T S Singh]

Can I take "dm" (say m=linspace(0,3,1000)) the independent variable and calculate the corresponding "a" (dependent variable) and plot??

[madhan ravi]

yes