How to remove some parts of a Matlab plot?

Hello,

I just wanted to know if it is possible to remove some parts of a Matlab plot. The solution is the specified region and below is the code,

clc;
clear;
close all;

w = -pi:0.01:pi;
r1 = 3;
r2 = 4;
x1 = 2.5;
y1 = -2;
x2 = 1;
y2 = 0.5;

x11 = x1+r1*cos(w);
y11 = y1+r1*sin(w);

x22 = x2+r2*cos(w);
y22 = y2+r2*sin(w);

x = -5:0.01:5;
yy1 = x-2;
yy2 = -x+2;

plot(x11,y11,'r',x22,y22,'b',x,yy1,'k',x,yy2,'k')
grid on
axis square

Answer 1

[Star Strider]

Try this:

w = -pi:0.01:pi;
r1 = 3;
r2 = 4;
x1 = 2.5;
y1 = -2;
x2 = 1;
y2 = 0.5;

x11 = x1+r1*cos(w);
y11 = y1+r1*sin(w);

x22 = x2+r2*cos(w);
y22 = y2+r2*sin(w);

x = -5:0.01:5;
yy1 = x-2;
yy2 = -x+2;

inred1 = inpolygon(x,yy1,x11,y11);
inred2 = inpolygon(x,yy2,x11,y11);
inblu1 = inpolygon(x,yy1,x22,y22);
inblu2 = inpolygon(x,yy2,x22,y22);
yy1(inred1 & inblu1) = NaN;
yy2(inred2 & inblu2) = NaN;

figure
plot(x11,y11,'r',x22,y22,'b',x,yy1,'k',x,yy2,'k')
grid on
axis equal

producing:

I changed the axis call to make the circles appear round.

[Pooya Zeg]

Thank you, and sorry for being unclear. I just wanted the opposite. I want to keep the region that your code removed and remove the other parts.

[Star Strider]

My pleasure!

That is easy!

Just change these two assignments:

yy1(inred1 & inblu1) = NaN;
yy2(inred2 & inblu2) = NaN;

to:

yy1(~(inred1 & inblu1)) = NaN;
yy2(~(inred2 & inblu2)) = NaN;

with the rest of the code unchanged,

producing:

The code works by creating logical vectors ‘inred#’ and ‘inblu#’ (where the # is the respective number). So to do the opposite simply requires using logical negation (the ~ operator) to reverse them.

EDIT — (03 Apr 2021 at 12:27)

Equivalently:

inboth1 = inred1 & inblu1;
inboth2 = inred2 & inblu2;

figure
plot(x11,y11,'r',x22,y22,'b',x(inboth1),yy1(inboth1),'k',x(inboth2),yy2(inboth2),'k')
grid on
axis equal

producing the same result.

The rest of the code is unchanged.

.

[Pooya Zeg]

Great! Thanks. It worked. I'm just wondering if this can also work for "contour."

[Star Strider]

As always, my pleasure!

With contour, likely not directly. It would be necessary to get the individual contours (difficult, hoiwever not impossible) and plot them separately, along with any other lines. Then a similar approach would likely work.

Note that contours, at least in my experience, do not overlap as the circles do here, so I have no idea how that would apply.