最好的方式转置data.table [英] best way to transpose data.table

问题描述

我经常需要转置一个 data.table ，每次它需要几行代码，我想知道是否有任何比我更好的解决方案。

I often need to transpose a data.table, every time it takes several lines of code and I am wondering if there's any better solution than mine.

如果我们使用示例表

library(data.table)
mydata <- data.table(col0=c("row1","row2","row3"),
                     col1=c(11,21,31),
                     col2=c(12,22,32),
                     col3=c(13,23,33))

mydata
# col0 col1 col2 col3
# row1   11   12   13
# row2   21   22   23
# row3   31   32   33

用 t（）转置它，它将转换为转换为字符类型的矩阵，而应用 data.table 到此矩阵将失去 row.names ：

and just transpose it with t(), it will be transposed to the matrix with conversion to character type, while applying data.table to such matrix will lose row.names:

t(mydata)
# [,1]   [,2]   [,3]  
# col0 "row1" "row2" "row3"
# col1 "11"   "21"   "31"  
# col2 "12"   "22"   "32"  
# col3 "13"   "23"   "33"  

data.table(t(mydata))
#   V1   V2   V3
# row1 row2 row3
#   11   21   31
#   12   22   32
#   13   23   33

所以我必须为此写一个函数：

so I had to write a function for this:

tdt <- function(inpdt){
  transposed <- t(inpdt[,-1,with=F]);
  colnames(transposed) <- inpdt[[1]];
  transposed <- data.table(transposed, keep.rownames=T);
  setnames(transposed, 1, names(inpdt)[1]);
  return(transposed);
}

 tdt(mydata)
# col0 row1 row2 row3
# col1   11   21   31
# col2   12   22   32
# col3   13   23   33

有什么我可以在这里优化或以更好的方式？ p>

is there anything I could optimize here or do it in "nicer" way?

推荐答案

为什么不只是熔化和 dcast data.table ？

library(reshape2)
dcast.data.table(melt(mydata, id.vars = "col0"), variable ~ col0)
#    variable row1 row2 row3
# 1:     col1   11   21   31
# 2:     col2   12   22   32
# 3:     col3   13   23   33

这篇关于最好的方式转置data.table的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！