MATLAB: Encounter an error while using fimplicit

MATLABplot

How to plot the following equation on matlab by using fimplicit?

(x-x0).*conj((x-x0))+(y-y0).^2=r^2

close all;

r=1./2;

x0=0;

y0=1./2;

syms x y

fimplicit((x-x0).*conj((x-x0))+(y-y0).^2-r^2)

axis equal

Matlab shows

'Undefined function or variable 'fimplicit'.'

Best Answer

The fimplicit function was introduced in R2016b.

Use the contour function instead:

r=1./2;
x0=0;
y0=1./2;
f = @(x,y) (x-x0).*conj((x-x0))+(y-y0).^2-r^2;
xv = linspace(x0-r, x0+r, 25);
yv = linspace(y0-r, y0+r, 25);
[X,Y] = ndgrid(xv,yv);
figure
contour(X,Y,f(X,Y), [0 0])
grid
axis equal

Related Solutions

MATLAB: How to do a surface plot with tangent plane

I believe the problem is that you need to vectorise the function, using element-wise operations in the multiplications and division as well as the exponentiations (that you already did). Otherwise, all that you need to do is to specify ‘x0’ and ‘y0’ as the values you want.

Try this:

f = @(x,y) (x.^2.*y + cos(x.*y))./(x.^2 + y.^2);
[xx,yy] = meshgrid(-5:0.25:5);
[fx,fy] = gradient(f(xx,yy),0.25);
x0 = 2;
y0 = 0;
t = (xx == x0) & (yy == y0);
indt = find(t);
fx0 = fx(indt);
fy0 = fy(indt);
z = @(x,y) f(x0,y0) + fx0*(x-x0) + fy0*(y-y0);
surf(xx,yy,f(xx,yy),'EdgeAlpha',0.7,'FaceAlpha',0.9)
hold on
surf(xx,yy,z(xx,yy))
plot3(1,2,f(1,2),'r*')

MATLAB: How to plot circle by one single equation

As one "equation" what does that mean? About the best I can offer is this:

r=2;
x0=0;
y0=0;
ezplot(@(x,y) (x-x0).^2 + (y-y0).^2 -r^2)
axis equal

Be careful that the units are equal for the two axes, else it ill not look circular.

I could also have done it using fimplicit.

r=2;
x0=0;
y0=0;
syms x y
fimplicit((x-x0).^2 + (y-y0).^2 -r^2)
axis equal

So, in either case, only one equation.

If you really insist on only one "variable, then you need to use a polar coordinate transformation. Thus, you can do it in terms of polar angle theta, as:

r=2;
x0=0;
y0=0;
theta = linspace(0,2*pi,100);
plot(x0 + r*cos(theta),y0 + r*sin(theta),'-')
axis equal

So only one variable, theta. If you are hoping for something else, something more or less, then you need to explain carefully what the goal is here.

Are you looking for a simple way to plot a circle? Perhaps try this:

cplot = @(r,x0,y0) plot(x0 + r*cos(linspace(0,2*pi)),y0 + r*sin(linspace(0,2*pi)),'-')

Now you have a little function that will plot a circle.

cplot(2,0,0)
hold on
cplot(3,1,2)
cplot(1,-1,1)
axis equal

Best Answer

Related Solutions

MATLAB: How to do a surface plot with tangent plane

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