R：如何重新定位价值？

Question

我有两个数据矩阵。

[2 0]

我想要的是将[2 1]中的列名与set.seed(1) df<-matrix(sample(1:1000, 20),nrow=4) colnames(df)<-c("V1","V2","V3","V4","V5") > df V1 V2 V3 V4 V5 [1,] 266 201 625 679 707 [2,] 372 894 62 380 976 [3,] 572 940 204 760 374 [4,] 906 657 175 491 763 loc<-c("V1","V3","V5","V4","V2", "V2","V4","V5","V3","V1", "V5","V1","V2","V4","V3", "V5","V3","V1","V2","V4") 中的列名进行比较，并按照df中的指示重定位loc中的值

我期望得到的结果应该像

df

任何帮助将不胜感激。谢谢！

Answer 1

可以选择使用sapply从loc的每一行中获取相应的列（基于df）。

m <- matrix(loc, byrow = TRUE, nrow = nrow(df))

result <- t(sapply(1:nrow(df), function(x)df[x,m[x,]]))

colnames(result) <- NULL

result
#      [,1] [,2] [,3] [,4] [,5]
# [1,]  266  625  707  679  201
# [2,]  894  380  976   62  372
# [3,]  374  572  940  760  204
# [4,]  763  175  906  657  491

Answer 2

您也可以这样做：

indices <- cbind( rep(1:nrow(df), each=ncol(df)), as.numeric(gsub("\\D", "", loc)) )
matrix(df[indices], nrow(df), byrow = TRUE)

#    [,1] [,2] [,3] [,4] [,5]
#[1,]  266  625  707  679  201
#[2,]  894  380  976   62  372
#[3,]  374  572  940  760  204
#[4,]  763  175  906  657  491