MATLAB: Finding closest distance between two data set for each point

closest distanceStatistics and Machine Learning Toolboxtwo data set

Hi,

I have two data set. Each of them have 300, 3D (x,y,z) data .

Assume;

first data set =m

second data set=n

Every point in "m" corresponds to 1 point in "n" which have to be the closest one.

I need to find the closest "n" to "m" and calculate the distance between them and i need to do it for all 300 data

I am new with matlab. I think i should use pdist2 but i could not find how.

Thank you…

Best Answer

d = pdist2(first_xyz, second_xyz);
[mindist, idx] = min(d, [], 2);

Here first_xyz and second_xyz should be something-by-3 arrays of x, y, z coordinates.

The idx that results will have as many rows as first_xyz has, and the value will be the index of which second_xyz row is closest to that point; the mindist value will tell you how close it is (no more computation will be required.)

If you want the index for each n (second dataset) as to which m it is closest to, then use min(d, [], 1)

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MATLAB: How to extract a value from 2-d matrix based on the row and column indexes

Define the targets variable and then run this on your data. The variable varAtTarget is your output.

This finds the nearest latitude and longitude coordinate to your target and returns the corresponding var value. However, I strongly urge you to rename the var variable since var() is a common Matlab function.

I added a couple extra steps to show how to print the outputs to the command window.

% Find the index to the closest lat and lon that equals the target values
targets = [-69.19, 35.17]; % [lon,lat] since you x seems to be Longitude and your y seems to latitudes
% Compute distance between targets and all (x,y) coordinates
d = pdist2(targets,[x(:),y(:)]); 
% Find the nearest coordinate
[minDist, minIdx] = min(d); 
% Output the corresponding var
varAtTarget = var(minIdx); 
% Get row,col number
[rowNum,colNum] = ind2sub(size(x),minIdx); 
% Output a summary text so you can determine whether the outputs make sense. 
fprintf(['The closest coordinates to target [%.2f, %.2f] is coordinate [%.2f, %.2f]\nat index %d '...
    '(row %d, col %d) which is at a distance of %.2f from the target.\nVar at that coordinate is %.2f.\n'], targets, ...
    x(minIdx), y(minIdx), minIdx, rowNum, colNum, minDist, varAtTarget)

Result:

MATLAB: How to calculate the shortest distance between points and a line

You can use the point_to_line_distance function.

Best Answer

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