![](/img/trans.png)
[英]R: How do I remove the first element from each inner element of a list without converting it to matrix?
[英]How do I compare each element in a list with each other element and outpt the results as a pairwise comparison matrix in R?
我正在嘗試為最近的植被研究中調查的每一對可能的地點自動計算 Jaccard 的相似性指數。
下面是我的數據格式的虛擬列表,其中 x、y 和 z 是離散的調查站點,function jaccard()
。
x <- c("sp1","sp2","sp3")
y <- c("sp2","sp3","sp4")
z <- c("sp3","sp4","sp5")
dummy_list <- list(x,y,z)
jaccard <- function(a, b) {
intersection = length(intersect(a, b))
union = length(a) + length(b) - intersection
return (intersection/union) }
我想將每個成對比較 (xy, xz, yz) 傳遞給jaccard()
和 output 計算的 Jaccard 指數矩陣。 我怎樣才能做到這一點?
我們可以先將您的Vectorize
jaccard
向量化,然后使用outer
:
x <- c("sp1","sp2","sp3")
y <- c("sp2","sp3","sp4")
z <- c("sp3","sp4","sp5")
dummy_list <- setNames(list(x, y, z), c("x","y","z"))
jaccard <- function(a, b) {
intersection = length(intersect(a, b))
union = length(a) + length(b) - intersection
return (intersection/union)
}
vjaccard <- Vectorize(jaccard)
outer(dummy_list, dummy_list, FUN = "vjaccard")
#> x y z
#> x 1.0 0.5 0.2
#> y 0.5 1.0 0.5
#> z 0.2 0.5 1.0
由reprex package (v2.0.1) 創建於 2022-03-02
jaccard <- function(List) {
ln <- combn(List, 2,function(x){
n <- length(intersect(x[[1]], x[[2]]))
m <- length(unlist(x))
n/(m-n)})
structure(ln, Size = length(ln), Diag = FALSE, class = 'dist')
}
jaccard(dummy_list)
1 2
2 0.5
3 0.2 0.5
我們可以使用以下基本 R 方法(不使用jaccard
function 但遵循相同的定義)
> dummy_list <- list(x = x, y = y, z = z)
> 1 / (outer(lengths(dummy_list), lengths(dummy_list), `+`) / crossprod(table(stack(dummy_list))) - 1)
x y z
x 1.0 0.5 0.2
y 0.5 1.0 0.5
z 0.2 0.5 1.0
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.