matlab中的快速二维直方图 [英] fast 2dimensional histograming in matlab
本文介绍了matlab中的快速二维直方图的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我为 2 个 matlab 向量编写了一个二维直方图算法.不幸的是,我无法弄清楚如何对其进行矢量化,而且对于我的需要来说,它的速度太慢了一个数量级.这是我所拥有的:
I have written a 2D histogram algorithm for 2 matlab vectors. Unfortunately, I cannot figure out how to vectorize it, and it is about an order of magnitude too slow for my needs. Here is what I have:
function [ result ] = Hist2D( vec0, vec1 )
%Hist2D takes two vectors, and computes the two dimensional histogram
% of those images. It assumes vectors are non-negative, and bins
% are the integers.
%
% OUTPUTS
% result -
% size(result) = 1 + [max(vec0) max(vec1)]
% result(i,j) = number of pixels that have value
% i-1 in vec0 and value j-1 in vec1.
result = zeros(max(vec0)+1, max(vec1)+1);
fvec0 = floor(vec1)+1;
fvec1 = floor(vec0)+1;
% UGH, This is gross, there has to be a better way...
for i = 1 : size(fvec0);
result(fvec0(i), fvec1(i)) = 1 + result(fvec0(i), fvec1(i));
end
end
想法?
谢谢!!约翰
推荐答案
这是我的 2D 直方图版本:
Here is my version for a 2D histogram:
%# some random data
X = randn(2500,1);
Y = randn(2500,1)*2;
%# bin centers (integers)
xbins = floor(min(X)):1:ceil(max(X));
ybins = floor(min(Y)):1:ceil(max(Y));
xNumBins = numel(xbins); yNumBins = numel(ybins);
%# map X/Y values to bin indices
Xi = round( interp1(xbins, 1:xNumBins, X, 'linear', 'extrap') );
Yi = round( interp1(ybins, 1:yNumBins, Y, 'linear', 'extrap') );
%# limit indices to the range [1,numBins]
Xi = max( min(Xi,xNumBins), 1);
Yi = max( min(Yi,yNumBins), 1);
%# count number of elements in each bin
H = accumarray([Yi(:) Xi(:)], 1, [yNumBins xNumBins]);
%# plot 2D histogram
imagesc(xbins, ybins, H), axis on %# axis image
colormap hot; colorbar
hold on, plot(X, Y, 'b.', 'MarkerSize',1), hold off
请注意,我删除了非负"限制,但保留了整数 bin 中心(这可以轻松更改为将范围划分为相同大小的指定数量的 bin,而不是分数").
Note that I removed the "non-negative" restriction, but kept integer bin centers (this could be easily changed into dividing range into equally-sized specified number of bins instead "fractions").
这主要受@SteveEddins 博客文章的启发
This was mainly inspired by @SteveEddins blog post.
这篇关于matlab中的快速二维直方图的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文