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Kdtree implementation in matlab

version 1.4 (59.4 KB) by

The code contains a kd tree implementation in Matlab

Updated

Most of the kdtree code for matlab has been implemented via mex files. I decided to come up with a purely matlab based implementation and so here it is .... The code is obviously expected to be slower than some of the c/c++ implementations that are out there but the fact that its implemented in matlab might make it useful in certain circumstances. Matlab doesnot have pointers and so i mimicked the pointer functionality by using a global cell array. I will appreciate any feedback on my submission ........

in functionn kd_closestpointfast
final_node=node_number; %the value assigned to variable "final_node" might be unused
why is that so?

Why I have this error:
Error using strcmp
Not enough input arguments.

when using my input of 12x12 matrix where the dimension I changed to 144.

JR

JR (view profile)

There seem to be some issues with the closestpointgood function. The following code shows that the distance according to this function is 0.0662 which is twice as much as the coordinates of another node: 0.0386.

X = 0.1321;
Y = 0.9393;
[index_vals,vector_vals,final_node] = kd_closestpointgood(tree,[X Y]);

X(2,1) = tree(final_node).nodevector(1,1);
Y(2,1) = tree(final_node).nodevector(1,2);
plot(X,Y,'linewidth',4);

%nearest node:
a = 0.1582 - X(1,1);
b = 0.9677 - Y(1,1);
c = sqrt(a^2+b^2)

%nearest node according to kd_closestpoint
a = X(1,1) - X(2,1);
b = Y(1,1) - Y(2,1);

c = sqrt(a^2+b^2)

kenza

kenza (view profile)

thank you for all kd codes. So, i have one question. I want use kd_knn for each 3D point of matrix (X). I built kd tree for matrix (X) and i want to find knn for each point of this matrix. In kd_knn code i can use only one point. Thank you for you help and suggestions.

Baoqiang Cao

Baoqiang Cao (view profile)

Just wonder any thoughts on parallelize this implementation if applicable?

David Navega

fzec

fzec (view profile)

I have some bugs while using the function kd_nclosestpoints. It throws errors about the number of elements that the members of the kdtree struct have. i.e.:

??? Error using ==> gt
Too many input arguments.

Error in ==> kd_nclosestpoints at 21
if(n>tree.numpoints)

I am using R2008a.

This is the same for tree.type, etc..

Thanks.

gurleen Sohi

gurleen Sohi (view profile)

hi..actually i need matlab code for the design of IIR filter low pass filter i.e magnitude and group delay using genetic algorithm in matlab...reply me on my email address gurleensohi@yahoo.com

C. Peng

C. Peng (view profile)

In addition, kd_nclosestpoints.m needs lots of change in order to use it. Even different type structure.

C. Peng

C. Peng (view profile)

the same in kd_closestpointfast.m line 66

although this program is good

Ilia Zveda

Ilia Zveda (view profile)

The same error also occurs on line 80.

Ilia Zveda

Ilia Zveda (view profile)

There is a bug in file kd_closestpointgood.m on lines 111 and 112
They are:
if (~isempty(tree_cell_2(node_number).left)) kd_closestpointgood(0,point,tree_cell_2(node_number).right);

Line 111 should instead check right not left:
if (~isempty(tree_cell_2(node_number).right))

Erik

Erik (view profile)

Works great.
As you say the other implementations out there makes use of mex files. This being pure m files and with w ell commentated code makes it easy to modify for altered use. I added a stored functionvalue at every node. Works great so far!

Well done!

Andrea Tagliasacchi

Andrea Tagliasacchi (view profile)

I didn't mean to give a 5/5 as I haven't tried it...
The form froze and it got ranked automatically...

Andrea Tagliasacchi

Andrea Tagliasacchi (view profile)

I haven't tried it but it's a very good idea, so people don't have to compile any source and still achieve some speedup.

I think you should provide comparison in terms of running time though. That will guide the visitors to make the correct choice...

 17 Feb 2010 1.4 Fixed a bug in the tree generation code ... and made corresponding changes in the other files 12 Feb 2010 1.2 Fixed a bug in kd_knn.m , Also wanted to acknowledge the contribution of Steven Michael 12 Feb 2010 1.1 Wanted to acknowledge some of the other submissions on the topic
MATLAB Release
MATLAB 7.4 (R2007a)