为什么我用ddply看到“错误：长度（行）== 1不为TRUE”？

Question

我有一个数据框，比如工资单，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)

我想通过PayBasis了解最高，最低和平均工资。我希望这可行：

ddply(payroll, "PayBasis", summarize)

但我得到一个错误：Error: length(rows) == 1 is not TRUE

我在这里缺少什么？

Answer 1

可能是因为你错误summarize代表summary（在这种情况下这不会像你期望的那样工作）。你可能想要：

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

请务必仔细查看?summarize和?ddply中的示例。