Is possible to make radius flexible within rangesearch function?

Hello everyone,

I meet an urgent situation, I have around 300000 points which has x and y coordinate and I want to find all neighbors near the specified a set of points which about 10000 points with flexible radius.

I tried to use 'rangesearch' function, but the radius in that function is fixed. Then I try to use for loop to get the result, but the execution time is too long because my data size.

My for loop is written as below

    %radius is a vector which length is 10000; data is a 300000-by-2 matrix,track is a 10000-by-2 matrix.
    for i=1:10002
        a=rangesearch(data,track,radius(i));
        idx(i)=a(i);
    end

So each track match a radius, and those 300000 points cut by different circle which has corresponding radius and center(track).

Anybody can help me simplified the code?

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency

Answer 1

[Andrew Rhodes]

Yuyi,

I had this same problem today while performing a range search. Through a little fiddling, I managed to find a solution. The trick is to turn everything into a cell and perform cellfun .

First we make an anonymous function that applies the range search

searcher = @(X, Y, Radius) rangesearch(X, Y, Radius);

Now let's convert all of your data to cells. The only caveat is that data, track, and radius must have the same height. So if you want to use a particular radius on multiple searches, you must repeat that element in the radius matrix. So given that data is size [n, 2], track is size [n, 2], and radius is size [n, 1]

DataCell = mat2cell(data, ones(length(data), 1), 2);
TrackCell = mat2cell(track, ones(length(track), 1), 2);
RadiusCell = num2cell(radius)

Now we can apply the cellfun to these cells with the ability for a flexible search radius.

Result = cellfun(searcher, DataCell, TrackCell, RadiusCell, 'Uni', 0);

where the 'Uni', 0 stands for 'UniformOutput', 'False' because the results may all be different lengths.

Hope this helps you and anyone else who finds it.