How to trim lines in plot?
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Hello, I'm trying to plot several lines in a circle and need to trim the part of lines which are out of this circle. So how can I do that? Thank you in advance
% plotting random lines
X1 = rand (8,8);
Y1 = rand (8,8);
figure
plot (X1,Y1)
hold on
% plotting the circle
R = 0.5;
angle = linspace(0,2*pi,180);
x= R*cos(angle);
y= R*sin(angle);
plot(x,y,'r')
axis equal
6 个评论
Rik
2018-3-14
Can you provide an example of what you mean? And what did you try already?
Lisa Smith
2018-3-14
Hi Rik, As shown in the picture, I need to delete all lines that are out of the circle and keep that inside it.
Walter Roberson
2018-3-14
Most of the time there will be a segment of the line in which one point is inside the circle and the other point is outside. Do you want to drop those segments, or do you want to calculate the intersection and draw just to the edge of the circle?
Will there be any line segments where both points are outside the circle but the line crosses the circle?
Lisa Smith
2018-3-14
Walter Roberson
2018-3-15
https://www.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections
https://www.mathworks.com/matlabcentral/fileexchange/11837-fast-and-robust-curve-intersections
https://www.mathworks.com/matlabcentral/fileexchange/8908-curve-intersect-2
Lisa Smith
2018-3-15
采纳的回答
Walter Roberson
2018-3-15
Not necessarily the best way, but a way that would work:
Take the coordinates of the random points, and subtract from them the coordinates of the center of the circle. Convert the result to polar coordinates. Now create a logical mask of the points that have r less than the radius of the circle.
Now you want to look at the boundaries between groups of points that are inside or not. Look for every transition between false (outside) and true (inside), and every transition between true (inside) and false (outside)
first_outside_in_group = [false, mask(1:end) & ~mask(2:end-1)];
last_outside_in_group = [mask(2:end) & ~mask(1:end-1), false];
keep = mask | first_outside_in_group | last_outside_in_group;
adjusted_theta = theta;
adjusted_r = r;
adjusted_r(first_outside_in_group) = R_circle;
adjusted_r(last_outside_in_group) = R_circle;
adjusted_theta(~keep) = nan;
adjusted_r(~keep) = nan;
[adjusted_x, adjusted_y] = pol2cart(adjusted_theta, adjusted_r);
adjusted_x = adjusted_x + circle_center_x;
adjusted_y = adjusted_y + circle_center_y;
and now you can plot(adjusted_x, adjusted_y)
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