r - tapply 函数提示 args 的长度不相等，但它们似乎匹配

Question

这里是失败的调用、错误消息和一些显示有问题的长度:

it <- tapply(molten, c(molten$Activity, molten$Subject, molten$variable), mean)
# Error in tapply(molten, c(molten$Activity, molten$Subject, molten$variable),  : 
#  arguments must have same length

length(molten$Activity)
# [1] 679734

length(molten$Subject)
# [1] 679734

length(molten$variable)
# [1] 679734

dim(molten)
# [1] 679734      4

str(molten)
# 'data.frame': 679734 obs. of  4 variables:
#  $ Activity: Factor w/ 6 levels "WALKING","WALKING_UPSTAIRS",..: 5 5 5 5 5 5 5 5 5 5 ...
#  $ Subject : Factor w/ 30 levels "1","2","3","4",..: 2 2 2 2 2 2 2 2 2 2 ...
#  $ variable: Factor w/ 66 levels "tBodyAcc-mean()-X",..: 1 1 1 1 1 1 1 1 1 1 ...
#  $ value   : num  0.257 0.286 0.275 0.27 0.275 ...

Answer 1

如果您查看 ?tapply，您会发现 X 应该是“一个原子对象，通常是一个向量”。您向 tapply 提供数据框(“molten”)，它不是原子对象。请参阅 is.atomic，并尝试 is.atomic(molten)。此外，您的分组变量应作为 list 提供(请参阅 INDEX 参数)。

这样的工作:

tapply(X = warpbreaks$breaks,  INDEX = list(warpbreaks$wool, warpbreaks$tension), mean)
#          L        M        H
# A 44.55556 24.00000 24.55556
# B 28.22222 28.77778 18.77778