How to use fimplicit with a symbolic function

I have a symbolic function r and am trying to plot it using fimplicit but I keep on getting an error in Matlab. I have tried switching up the symbolic r function, but it isn't working no matter what I try. Any suggestions?

This is a school assignment, so no complete answers.

syms x y R
r=(((x-2).^2)+((y-4).^2)==R.^2);
z=(x/2)+1;

[xc,yc]=solve(((x-2).^2)+(y-4).^2==R^2, (x/2)+1==y)

%(b)
subs(r,R,2)
hold on
fimplicit(((x-2).^2)+((y-4).^2)-R.^2)
fimplicit(z)
hold off

Answer 1

[Matt J]

Using matlabFunction, you can derive a non-symbolic version of your circle equation expression from the symbolic version,

>> circ=(((x-2).^2)+((y-4).^2)-R.^2)
 
circ =
 
(x - 2)^2 + (y - 4)^2 - R^2
 
>> circ_nonsym=matlabFunction(subs(circ,R,2))

circ_nonsym =

  function_handle with value:

    @(x,y)(x-2.0).^2+(y-4.0).^2-4.0

The latter can be used with fimplicit

>> fimplicit(circ_nonsym); shg