How to calculate Euclidian distance between two points defined by matrix containing x, y?

Question

I am very lost in Euclidean distance calculation. I have found functions dist2{SpatialTools} or rdist{fields} to do this, but they doesn´t work as expected. I suppose that one point has two coordinates in carthesian system, so [x,y]. To measure distance between 2 points (defined by row), I need 4 coordinates for 2 points, so point A: [x1,y1] point B: [x2,y2] Points coordinations: ``` A[0,1] B[0,0] C[1,1] D[1,1] ``` I have two matrices: x1(A and C are there, defined by rows) and x2 (contain B and D). Written in matrix: ``` library("SpatialTools") x1<-matrix(c(0,1,1,1), nrow = 2, ncol=2, byrow=TRUE) x2<-matrix(c(0,0,1,1), nrow = 2, ncol=2, byrow=TRUE) ``` so I obtain ``` > x1 [,1] [,2] [1,] 0 1 #(as xy coordinates of A point) [2,] 1 1 #(same for C point) > x2 [,1] [,2] [1,] 0 0 #(same for B point) [2,] 1 1 #(same for D point) ``` To calculate euclidean distance between ``` A <-> B # same as x1[1,] <-> x2[1,] C <-> D # same as x1[2,] <-> x2[2,] ``` I assume to obtain EuclidDist: ``` > x1…

Accepted Answer

If you just want a vector, something like this will work for you.

Try something like this:

```
euc.dist <- function(x1, x2) sqrt(sum((x1 - x2) ^ 2))

library(foreach)
foreach(i = 1:nrow(x1), .combine = c ) %do% euc.dist(x1[i,],x2[i,])
```

This will work for any dimensions.

If you don't want to use foreach, you can use a simple loop:

```
dist <- NULL
for(i in 1:nrow(x1)) dist[i] <- euc.dist(x1[i,],x2[i,])
dist
```

Although, I would recommend foreach (because it's very easy to for various tasks like this). Read more about it in the documentation of the package.

How to calculate Euclidian distance between two points defined by matrix containing x, y?

Solution

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