vec <- c(rep(0, 75), rep(1, 25))
n <- 25
to_change <- sample(which(vec == 0), n)
modified_vec <- vec
modified_vec[to_change] <- 1
就像這樣。你可以把它包裝在一個函數中。
而你應該真的在apply
的矩陣中做,而不是for循環。
這個小例子是很容易看到它的工作:
n_vecs <- 5
vec_length <- 10
n_0 <- 7 # Number of 0's at the start of each vector
vec_mat <- matrix(c(rep(0, n_vecs * n_0), rep(1, n_vecs * (vec_length - n_0))),
nrow = vec_length, ncol = n_vecs, byrow = T)
> vec_mat
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 0 0 0 0 0
[3,] 0 0 0 0 0
[4,] 0 0 0 0 0
[5,] 0 0 0 0 0
[6,] 0 0 0 0 0
[7,] 0 0 0 0 0
[8,] 1 1 1 1 1
[9,] 1 1 1 1 1
[10,] 1 1 1 1 1
change_n_0 <- function(x, n) {
x_change <- sample(which(x == 0), n)
x[x_change] <- 1
return(x)
}
vec_mat <- apply(vec_mat, MARGIN = 2, FUN = change_n_0, n = 2)
> vec_mat
[,1] [,2] [,3] [,4] [,5]
[1,] 1 1 0 0 1
[2,] 0 0 0 1 0
[3,] 0 0 0 0 0
[4,] 0 0 0 0 0
[5,] 0 0 1 0 1
[6,] 0 1 0 1 0
[7,] 1 0 1 0 0
[8,] 1 1 1 1 1
[9,] 1 1 1 1 1
[10,] 1 1 1 1 1
你可以在一開始大如你想擴展的常量。
你真的不應該使用'c'作爲變量名稱,因爲它也是最常用函數的名稱。 – Gregor