CODEWITHSUNDEEP
matlabsortingplot
user813853
user813853

Reputation:

Draw a curve correctly using Matlab?

I have a couple of data x0 and y0 that corresponds to curve. It contains 8 points, for example : K(x0(2),y0(2)).

The problem is that when I plot x0 and y0 like this : 

plot(x0,y0,'c*');
plot(x0,y0,'k');

I get the cyan point at a good place, but the curve is a mess. Check the screenshot:

enter image description here

Can I do some sort of Sorting ?

This question seems simple but I am a newbie.

Upvotes: 1

Views: 124

Answers (2)

rayryeng
rayryeng

Reputation: 104545

If you have the Mapping Toolbox, the function poly2ccw also performs the job for you. Convex Hull is a more general purpose algorithm to handle any convex polygon. If you already have the extremities of your shape, you can simply use poly2ccw return coordinates reordered that will allow you to draw the perimeter of the shape in counter-clockwise order.

Specifically, you would just do this:

[x1, y1] = poly2ccw(x0, y0);

x1 and y1 would contain the shuffled points of x0 and y0 so that they are now in counter-clockwise order. You can then draw them via:

plot(x1, y1, 'k');

Upvotes: 0

Matt
Matt

Reputation: 13953

Since the points define a convex polygon, you can simply use the convhull-function for this. convhull returns the indexes of the outermost points in x0 and y0. For this question we exploit that they are arranged counter-clockwise around the hull, so you can plot them nicely after.

h = convhull(x0,y0);
plot(x0(h),y0(h),'k');

The result looks like this:

result

Points used to generate the output:

x0 = [1 2 3 4 4 3 2 1];
y0 = [2 3 0 2 1 3 0 1];

Upvotes: 3

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