从矢量样本创建数据帧

Question

假设我们有一个向量v <- 1:3，我们希望通过将sample函数应用到v来生成一个包含5行的数据帧。预期结果应该是这样的：

X1  X2  X3
1   3   2
2   3   1
3   1   2
2   1   3
3   2   1

注意：如果某些行重复，则无关紧要。我更喜欢不需要forloop的解决方案。

Answer 1

v = 1:3
data.frame(matrix(sample(v, 5*length(v), replace = T), nrow = 5, ncol = length(v)))
#  X1 X2 X3
#1  3  3  1
#2  1  1  3
#3  3  3  1
#4  2  2  1
#5  3  1  2

# else 
data.frame(t(replicate(5, sample(v, length(v), replace = F))))
# else 
data.frame(t(sapply(1:5, function(x) sample(v, length(v), replace = F))))

Answer 2

我认为pryr＆＃39; %<a-%运算符非常适合这一点。 %<a-%将表达式保存到变量中，但每次计算变量时，表达式都会重新运行。非常适合采样：

library(pryr)
#the function sample will be rerun each time sampled is evaluated
sampled %<a-% sample(v)

#replicate just replicates an expression
#t pivots the matrix, so that you get the output you want
data.frame(t(replicate(5, sampled)))

#or simply (since the edit makes it simpler)
#data.frame(t(replicate(5, sample(v))))

输出：

  X1 X2 X3
1  3  1  2
2  2  1  3
3  1  3  2
4  2  3  1
5  2  3  1

Answer 3

dfV <- data.frame(v1 = sample(v, 5,replace = TRUE), v2 = sample(v, 5, replace = TRUE), v3 = sample(v, 5, replace = TRUE))