将属性向量转换为具有元素差异的矩阵 [英] Transform attribute vector into a matrix with differences of elements

问题描述

类似于此以前的帖子，我需要从属性向量转换成矩阵.这次是使用R的成对元素之间的差异.

Similarly to this previous post I need to transfrom an attribute vector into a matrix. This time with differences between pairs of elements using R.

例如，我有一个向量，该向量报告了N人的年龄(18至90岁).我需要将此向量转换为名为A的NxN矩阵(行和列上都有人的名字)，其中每个单元格Aij的值均为| age_i-age_j |的值，代表两个人i和j之间年龄的绝对差异.

For example I have a vector which reports the age of N people (from 18 to 90 years). I need to convert this vector into a NxN matrix named A (with people names on rows and columns), where each cell Aij has the value of |age_i-age_j|, representing the absolute difference in age between the two people i and j.

这里有一个3个人的例子，第一人18岁，第二人23岁，第三人60岁，他们产生了这个向量:

Here is an example with 3 persons, first 18 yo, second 23 yo, third 60 yo, which produce this vector:

c(18, 23, 60) 

我想将其转换为这个矩阵:

I want to transform it into this matrix:

A = matrix( c(0, 5, 42, 5, 0, 37, 42, 37, 0), nrow=3, ncol=3, byrow = TRUE) 

推荐答案

tmp <- c(18, 23, 60)

您可以将dist与两个参数一起使用:

You can use dist with a couple of arguments:

dist(tmp, upper=TRUE, diag=TRUE)
   1  2  3
1  0  5 42
2  5  0 37
3 42 37  0

请注意，dist函数返回一个"dist"对象，因此您可能需要使用as.matrix将其强制转换为矩阵.然后，您可以删除参数:

Note that the dist function returns a "dist" object, so you might want to coerce it to a matrix with as.matrix. Then you can drop the arguments:

as.matrix(dist(tmp))
   1  2  3
1  0  5 42
2  5  0 37
3 42 37  0

或再次使用outer.给它减去减法运算符，然后取绝对值.

Or again use outer. Feed it the subtraction operator, then take the absolute value.

abs(outer(tmp, tmp, "-"))

     [,1] [,2] [,3]
[1,]    0    5   42
[2,]    5    0   37
[3,]   42   37    0

推测dist将比outer快，因为该算法可以利用这种计算中存在的对称性，而outer更通用.

Presumably, dist will be faster than outer, since the algorithm can take advantage of the symmetry that is present in such a calculation, while outer is more general.

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