互动表-宠物和房屋的情况 [英] Table of Interactions - Case with pets and houses

问题描述

我有一个房屋清单和一个动物物种清单。

I have a list of houses and a list of animal species.

houses = c(1,1,2,3,4,4,4,4,5,6,5)
animals = c('cat','dog','cat','dog','rat', 'cat', 'spider', 'snake', 'cat', 'cat', 'rat')

我正在尝试创建一个函数，该函数返回上面的三角表，该三角表为每只宠物指示观察到的宠物与其他动物相比在同一房屋中生活的次数。

I am trying to create a function that returns an upper triangular table that indicates for each pet, the number of times that it was observed to live in the same house than the other animal species. Does it make sense?

对于上面的示例，表应如下所示（希望没有错误！）：

For the above example, the table should look like this (hope there's no mistake!) :

    dog   rat   spider   snake
cat  1     2      1        1      
dog        0      0        0
rat               1        1
spider                     1

---

注意：此函数适用于两个相同长度的向量，不管它们包含数字还是字符串

---

Note: This function should work for any two vectors of same lengths, whatever if they contain numbers or string

推荐答案

使用表和 crossprod ：

out <- crossprod(table(houses, animals))
out[lower.tri(out, diag=TRUE)] <- NA
out
#         animals
# animals  cat dog rat snake spider
#   cat     NA   1   2     1      1
#   dog     NA  NA   0     0      0
#   rat     NA  NA  NA     1      1
#   snake   NA  NA  NA    NA      1
#   spider  NA  NA  NA    NA     NA

由于输出是 matrix ，因此可以直接在< NA 中取消打印 NA 值。 code> print ：

Since the output is a matrix you can suppress the printing of the NA values directly in print:

print(out,na.print="")
#         animals
# animals  cat dog rat snake spider
#   cat          1   2     1      1
#   dog              0     0      0
#   rat                    1      1
#   snake                         1
#   spider                         

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