nearestNeighbor

Vertex closest to specified point

collapse all in page

Syntax

ID = nearestNeighbor(TR,P)
ID = nearestNeighbor(TR,x,y)
ID = nearestNeighbor(TR,x,y,z)
[ID,d] = nearestNeighbor(___)

Description

ID = nearestNeighbor(TR,P) returns the IDs of the vertices closest to the query points in P. Each row in the matrix P contains the coordinates of a query point.

example

ID = nearestNeighbor(TR,x,y) specifies the x-coordinates and y-coordinates of 2-D query points as separate column vectors.

ID = nearestNeighbor(TR,x,y,z) specifies the x-coordinates, y-coordinates, and z-coordinates of 3-D query points as separate column vectors.

example

[ID,d] = nearestNeighbor(___) also returns the Euclidean distance between each query point and its nearest neighbor for any of the previous syntaxes.

example

Examples

collapse all

Open Live Script

Compute the nearest neighbors in a 3-D triangulation.

Create a 3-D Delaunay triangulation.

P = [1 1 0;
    -1 1 0;
    -1 -1 0;
     1 -1 0;
     0 0 2;
     0 0 0];
TR = delaunayTriangulation(P);

Plot the triangulation and a query point.

tri = TR(:,:);
trisurf(tri,P(:,1),P(:,2),P(:,3),FaceAlpha=0.5)
hold on
x = 0;
y = -0.5;
z = 2;
plot3(x,y,z,"k*")

Figure contains an axes object. The axes object contains 2 objects of type patch, line. One or more of the lines displays its values using only markers

Find the coordinates of the nearest neighbor to the query point. 

ID = nearestNeighbor(TR,x,y,z);
C = TR.Points(ID,:)
C = 1×3

     0     0     2
Open Live Script

Compute the nearest neighbors in a 2-D triangulation.

Create a 2-D triangulation.

C = [5 3 1;
     3 2 1;
     3 4 2;
     4 6 2];
TP = [2.5 8.0;
      6.5 8.0;
      2.5 5.0;
      6.5 5.0;
      1.0 6.5;
      8.0 6.5];
TR = triangulation(C,TP);

Define two query points.

P = [2 4; 6 6.5];

Plot the triangulation and the query points.

triplot(TR)
hold on
plot(P(:,1),P(:,2),"k*")
ylim([1.5 8.5])
xlim([0.5 8.5])

Figure contains an axes object. The axes object contains 2 objects of type line. One or more of the lines displays its values using only markers

Find the nearest neighbors to the query points and the distances between them.

[ID,d] = nearestNeighbor(TR,P);

Highlight in red the points in the triangulation that are the nearest neighbors to the query points.

N = TP(ID,:);
plot(N(:,1),N(:,2),"*r")

Figure contains an axes object. The axes object contains 3 objects of type line. One or more of the lines displays its values using only markers

Display the distance between each query point and its nearest neighbor.

d
d = 2×1

    1.1180
    1.5811

Input Arguments

collapse all

Triangulation representation, specified as a scalar triangulation or delaunayTriangulation object. nearestNeighbor does not support delaunayTriangulation objects with constrained edges.

Data Types: triangulation | delaunayTriangulation

Query points, specified as a matrix with 2 or 3 columns. P contains the x-coordinates, y-coordinates, and (possibly) z-coordinates of the query points.

Data Types: double

x-coordinates of query points, specified as a column vector.

Data Types: double

y-coordinates of query points, specified as a column vector.

Data Types: double

z-coordinates of query points, specified as a column vector.

Data Types: double

Output Arguments

collapse all

Vertex IDs of the nearest neighbors to the query points, returned as a column vector. A vertex ID is the row number of the corresponding vertex in the Points property.

Data Types: double

Euclidean distances from the query points to their nearest neighbors, returned as a column vector the same length as ID.

Data Types: double

Extended Capabilities

expand all

Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Version History

Introduced in R2013a

expand all

See Also

|