R语言 长型数据与矩阵数据互换

一一对应 转换为 矩阵

tmp <- data.frame(ID1 = c("x","x","y"),
                  ID2 = c("x","y","x"),
                  var = c(1,2,3) )
 #  ID1 ID2 var
#1   x   x   1
#2   x   y   2
#3   y   x   3
library(tidyr)
spread_tmp = spread(tmp, ID2, var)
#  ID1 x  y
#1   x 1  2
#2   y 3 NA

矩阵转为长条，就是常见的melt了

library(reshape)
melt(spread_tmp,variable_name = "ID2",  )
#  ID1 ID2 value
#1   x   x     1
#2   y   x     3
#3   x   y     2
#4   y   y    NA

请注明来源：https://www.jianshu.com/p/bb9ccffd9dd5