CODEWITHSUNDEEP
matlabfindmeshsurfacevertex
amine
amine

Reputation: 19

Use of Matlab find function for getting index of a vertex using its coordinates

I have a matrix 50943x3 that contains vertices of a surface mesh.I want to find the index of a certain vertex using its coordinates (x,y,z).

I tried the Matlab function find but it return an empty matrix 0-by-1.

Thanks in advance,

Cheers

Upvotes: 0

Views: 519

Answers (2)

Brice
Brice

Reputation: 1580

Try the following:

mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));

What it does: == or eq will check if coordinates are equal (gives a [50943x3] bool matrix) all will return true only if all coordinates are equal find returns the index of all non zero elements

This works only for an exact match (hence the integer coordinates picked with randi).

Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.

[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point

Upvotes: 1

Zep
Zep

Reputation: 1576

Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:

% Your matrix
M = randn(50943 , 3);

% The coordinates you are looking for
P = [0,0,0];

% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));

% Closest coordinates to target
[~ , pos] = min(D);

% Display result
disp(M(pos , :))

Upvotes: 2

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