Matlab-2D浓度/轮廓图

Question

2D matlab Contour plot - concentration map

I have two sets of data

x = (x1, x2, x3....) y = (y1, y2, y3....)

which describe the cartesian co-ordinates of a set of points in the plane. So x1y1 is the coordinate of object 1 and so on.

The coordinates are restricted to certain values: a minimum (0) and maximum value which describe the dimensions of the plane (which is a rectangle).

For example, the coordinates might describe the position of objects in a room, or trees in a field or so on.

How can I represent these co-ordinates (the two sets of data) as a 2D contour/concentration plot using matlab? ie rather than just dots on the plane (a scatter graph) a smooth continuous colour map/

kind regards W

Answer 1

It is not really obvious what you are asking. Remember for making a contour you need another set of data besides x and y.

I think what you are trying to achieve can be done using meshgrid which gives you a proper mesh on your data:

x = rand(1,20);
y = rand(1,20);
[X,Y]=meshgrid(x,y);
Z = zeros(size(X));
mesh(X,Y,Z);

Answer 2

Generate a matrix where every value is a coordinate region and add 1 for every point in that region.

So for example you have points (0.5,0.7) (0.9,0.8) (1.5,0.6) (1.8,1.2)

And you map this to a matrix where every value corresponds to a "square" of a value region 1x1.

a(1,1) = everything in the region 0 <= x < 1, 0 <= y < 1
a(1,2) = everything in the region 0 <= x < 1, 1 <= y < 2
a(2,1) = everything in the region 1 <= x < 2, 0 <= y < 1
a(2,2) = everything in the region 1 <= x < 2, 1 <= y < 2

So you would get [2 1;0 1] and then you can contour it.

If you need a finer resolution just decrease the mapping size.

I can't give you a code solution on the fly because my Matlab is a bit rusty, but the principle should work fine.