r - 为什么我在 ddply 中看到 "Error: length(rows) == 1 is not TRUE"？

Question

我有一个数据框，比如工资单，例如:

payroll <- read.table(text="
AgencyName          Rate             PayBasis     Status    NumRate
HousingAuthority    $26,843.00   Annual           Full-Time 26843.00
HousingAuthority    $14,970.00   ProratedAnnual   Part-Time 14970.00
HousingAuthority    $26,843.00   Annual           Full-Time 26843.00
HousingAuthority    $14,970.00   ProratedAnnual   Part-Time 14970.00
HousingAuthority    $13.50           Hourly           Part-Time 13.50
HousingAuthority    $14,970.00   ProratedAnnual   Part-Time 14970.00
HousingAuthority    $26,843.00   Annual           Full-Time 26843.00", header = TRUE)

“NumRate”实际上是数字:

payroll$NumRate <- as.numeric(payroll$NumRate)

我想了解 PayBasis 的最高、最低和平均工资。我希望这能起作用:

ddply(payroll, "PayBasis", summarize)

但是我收到了一个错误:错误:length(rows) == 1 is not TRUE

我在这里缺少什么？

Answer 1

可能是因为您将 summarize 误认为 summary(在这种情况下，它不会像您期望的那样工作)。您可能想要:

ddply(payroll, "PayBasis", summarize,mx = max(NumRate),mn = min(NumRate),avg = mean(NumRate))
        PayBasis      mx      mn     avg
1         Annual 26843.0 26843.0 26843.0
2         Hourly    13.5    13.5    13.5
3 ProratedAnnual 14970.0 14970.0 14970.0

并且请务必仔细查看 ?summarize 和 ?ddply 中的示例。