R中的有符号距离矩阵 [英] Signed distance matrix in R

问题描述

[注意，我写下了这个问题，然后找到了答案.我以为也许其他人想知道这一点，所以我发布答案是为了以防万一.我不确定这是否是完成的事情"].

[Note, I wrote out this question, then found an answer. I thought maybe someone else would like to know it, so I'm posting the answer just in case. I'm not sure if this is the "done thing"].

假设我想要向量的有符号距离矩阵，即距离并不总是正的，而是可以是负的.您不能使用

Suppose I want the signed distance matrix of a vector, i.e. the distance's aren't always positive, but can be negative. You can't use

dist()

因为它返回绝对值.

推荐答案

这是另一种方法，它更快并且需要更少的内存:

Here's another approach, which is much faster and needs less memory:

y <- sample (1 : 4)
distmat <- outer (y, y, `-`) 

产量:

> distmat
     [,1] [,2] [,3] [,4]  
[1,]    0    1    3    2  
[2,]   -1    0    2    1  
[3,]   -3   -2    0   -1  
[4,]   -2   -1    1    0

## not sure why you want the upper triangular NA
distmat[upper.tri(distmat,diag=TRUE)]<-NA

但您可能想要:

> as.dist (distmat)
   1  2  3
2 -1      
3 -3 -2   
4 -2 -1  1

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