以下是失败的调用、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 ...