R-重塑-熔化错误 [英] R - Reshape - Melt Error

问题描述

我正在尝试融化一个数据框，但我收到了这个奇怪的错误。知道为什么吗？

str(zx7)
'data.frame':   519 obs. of  5 variables:
 $ calday.new: Date, format: "2011-01-03" "2011-01-04" "2011-01-05" "2011-01-06" ...
 $ A20    : Time-Series  from 1 to 519: 0 0 0 0 0 0 0 0 0 0 ...
 $ B20    : Time-Series  from 1 to 519: 0 0 0 0 0 0 0 0 0 0 ...
 $ C20    : Time-Series  from 1 to 519: 0 0 0 0 0 0 0 0 0 0 ...
 $ D20    : Time-Series  from 1 to 519: 0 0 0 0 0 0 0 0 0 0 ...

zx7.melt <- melt(zx7, id=c("calday.new"))
Error in `[<-.ts`(`*tmp*`, ri, value = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  : only replacement of elements is allowed

推荐答案

问题是旧的"重塑"包的melt()函数在遇到类ts的对象时不知道该怎么办。

因此，您有两个明显的选择(尽管可能还有更多)：

1. unclass您之前melt()当前分类为ts的变量：

   zx7b <- zx7         # Make a backup, just in case
   library(reshape)    # Notice this is "reshape", not "reshape2"
   head(melt(zx7b, id=c("calday.new"))) # Doesn't work
   # Error in `[<-.ts`(`*tmp*`, ri, value = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  : 
   #   only replacement of elements is allowed
   
   ## Unclass the relevant columns from your data.frame
   zx7b[sapply(zx7b, is.ts)] <- lapply(zx7b[sapply(zx7b, is.ts)],
                                       unclass)
   head(melt(zx7b, id=c("calday.new")))
   #   calday.new variable value
   # 1 2011-01-03      A20     0
   # 2 2011-01-04      A20     0
   # 3 2011-01-05      A20     0
   # 4 2011-01-06      A20     0
   # 5 2011-01-07      A20     0
   # 6 2011-01-08      A20     0
   

2. 改为升级到"reshape2"，不需要取消分类。

   library(reshape2) # Notice that this is reshape2!
   head(melt(zx7, id=c("calday.new"))) # Melt the original data.frame
   #   calday.new variable value
   # 1 2011-01-03      A20     0
   # 2 2011-01-04      A20     0
   # 3 2011-01-05      A20     0
   # 4 2011-01-06      A20     0
   # 5 2011-01-07      A20     0
   # 6 2011-01-08      A20     0
   

我没有花时间来做这件事，但是您可以检查melt()的melt.data.frame方法的代码，看看不同之处在哪里。安装这两个程序包，然后键入reshape2:::melt.data.frame和reshape:::melt.data.frame以查看基础函数。

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