Question

使用plyr包汇总我的数据时，似乎不可能使用nlevels（）函数。

我的数据集结构如下：

>aer <- read.xlsx("XXXX.xlsx", sheetIndex=1)
>aer$ID <- as.factor(aer$ID)
>aer$description <- as.factor(aer$description)    
>head(aer)

  ID SOC   start        end         days  count severity relation
1  1 410   2015-04-21   2015-04-28    7     1        1        3
2  1 500   2015-01-30   2015-05-04   94     1        1        3
3  1 600   2014-11-25   2014-11-29    4     1        1        3
4  1 600   2015-01-02   2015-01-07    5     1        1        3
5  1 600   2015-01-26   2015-03-02   35     1        1        3
6  1 600   2015-04-14   2015-04-17    3     1        1        3

> dput(head(aer,4))
structure(list(ID = structure(c(1L, 1L, 1L, 1L), .Label = c("1", 
"2", "3", "4", "5", "6", "7", "8", "9", "10", "12", "13", "14", 
"15"), class = "factor"), SOC = c(410, 500, 600, 600),  
start = structure(c(16546, 16465, 16399, 16437), class = "Date"), 
end = structure(c(16553, 16559, 16403, 16442), class = "Date"), 
days = c(7, 94, 4, 5), count = c(1, 1, 1, 1), severity = c(1, 
1, 1, 1), relation = c(3, 3, 3, 3)), .Names = c("ID", "SOC", 
"description", "start", "end", "days", "count", "severity", "relation"
), row.names = c(NA, 4L), class = "data.frame")

我想知道的是＆＃34; ID＆＃34;在使用变量＆＃34; SOC＆＃34;来划分数据集时创建的数据部分中的变量。我想将这些信息与新数据集中的一些其他变量一起汇总。因此，我想像这样使用plyr包：

summaer2 <- ddply(aer, c("SOC"), summarise,
    participants    = nlevels(ID), 
    events          = sum(count),
    min_duration    = min(days), 
    max_duration    = max(days),
    max_severity    = max(severity))

这会返回以下错误：

Error in Summary.factor(c(4L, 5L, 11L, 11L, 14L, 14L), na.rm = FALSE) : 
‘max’ not meaningful for factors

有人可以就如何实现目标向我提出建议吗？或者我做错了什么？

非常感谢提前！

Answer 1

<强>更新

用nlevels(ID)代替length(unique(ID))似乎给了我想要的输出：

> head(summaer2)
   SOC participants events min_duration max_duration max_severity
1  100            4      7            1           62            2
2  410            9     16            1           41            2
3  431            2      2          109          132            1
4  500            5      9           23          125            2
5  600            8     19            1           35            1
6 1040            1      1           98           98            2

使用nlevels（）进行R-ddply总结不起作用

1 个答案: