Making a contour plot from x and y data
显示 更早的评论
I have a two column vector containing x and y values. The y values have a high accuracy (many decimal points).
x ranges from 0 to 50000 and y from 0 to 14.
I need to use contourf to make a 2d representation of this data.
How can this be done?
6 个评论
jonas
2020-7-21
I need to use contourf to make a 2d representation of this data.
What do you mean by x and y - data? contourf is a 2d representation of three dimensional data. Perhaps you are missing an array?
Adam Danz
2020-7-21
Contour plots are 2D representations of 3D data. x and y define the first 2 dimensions but what will define the 'height' or the 3rd dimension of your contour plot? Are you looking for a bivariate distribution of your (x,y) values (histogram2)?
Check out the first example of the contour function to get a sense what it does.
Adam Danz
2020-7-21
Ha! Nearly identical comments written simultaneously.
Markus Similä
2020-7-22
KSSV
2020-7-22
Share your data.
Markus Similä
2020-7-22
采纳的回答
The bivariate density can be computed using histcounts2. You'll need to specify either the number of bins or the bin edges for the x and y variables using one of the syntaxes below.
Here's what the solution will look like. xy is your nx2 matrix of [x,y] values.
[N,Xedges,Yedges] = histcounts2(xy(:,1), xy(:,2), 5);
% or use [N,Xedges,Yedges] = histcounts2(X,Y,Xedges,Yedges);
% Compute bin centers
Xcnt = Xedges(2:end) - abs(diff(Xedges(1:2))/2);
Ycnt = Yedges(2:end) - abs(diff(Yedges(1:2))/2);
figure()
contour(Xcnt,Ycnt, N)
% show bins
xlim = [min(Xedges),max(Xedges)];
ylim = [min(Yedges),max(Yedges)];
arrayfun(@(x)xline(x,'Color',[.8 .8 .8]),Xedges)
arrayfun(@(y)yline(y,'Color',[.8 .8 .8]),Yedges)
% colorbar
cb = colorbar();
ylabel(cb,'density')
更多回答（1 个）
KSSV
2020-7-22
0 个投票
I would follow like below:
- You need to generate z values which are density values.
- I would fix a distance r and calculate the number of points within r for each point using rangesearch.
- Now you can use scatter to plot the density values.
- If your data is structured arrange the data and use contourf.
类别
在 帮助中心 和 File Exchange 中查找有关 Contour Plots 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
