获取向量 数组中元素对应的索引号或者下标号

genechip

获取下标号的函数是which()
which(x, arr.ind = FALSE)Arguments

x	a logical vector or array. NAs are allowed and omitted (treated as if FALSE)
arr.ind	logical; should array indices be returned when x is an array?

Exampleswhich(LETTERS == "R")
which(ll <- c(TRUE,FALSE,TRUE,NA,FALSE,FALSE,TRUE))#> 1 3 7
names(ll) <- letters[seq(ll)]
which(ll)which((1:12)%%2 == 0) # which are even?
which(1:10 > 3, arr.ind=TRUE)
( m <- matrix(1:12,3,4) )
which(m %% 3 == 0)
which(m %% 3 == 0, arr.ind=TRUE)
rownames(m) <- paste("Case",1:3, sep="_")
which(m %% 5 == 0, arr.ind=TRUE)
dim(m) <- c(2,2,3); m
which(m %% 3 == 0, arr.ind=FALSE)
which(m %% 3 == 0, arr.ind=TRUE)
vm <- c(m)
dim(vm) <- length(vm) #-- funny thing with  length(dim(...)) == 1
which(vm %% 3 == 0, arr.ind=TRUE)