为什么我会看到“错误:length(rows)== 1不是TRUE"；与ddply? [英] Why am I seeing "Error: length(rows) == 1 is not TRUE" with ddply?

问题描述

我有一个数据框，例如工资单，例如:

I have a data frame, say payroll, like:

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:

The "NumRate" is actually numeric:

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

我想了解PayBasis的最高，最低和平均工资.我希望这能奏效:

And I'd like to get a know the max, min and mean salaries by PayBasis. I expect this to work:

ddply(payroll, "PayBasis", summarize)

但是我收到一个错误消息:Error: length(rows) == 1 is not TRUE

But instead I'm getting an error: Error: length(rows) == 1 is not TRUE

我在这里想念什么?

推荐答案

可能是因为您将summarize误认为summary(在这种情况下无法正常工作).您可能想要:

Probably because you've mistaken summarize for summary (which won't work like you expect in this context). You probably wanted:

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

并确保更仔细地查看?summarize和?ddply中的示例.

And be sure to look more carefully at the examples in ?summarize and ?ddply.

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