如何在数据框架上使用强制转换？

Question

我有一个如下数据框:

  year income    group
1  2008  27907  Under25
2  2009  25522  Under25
3  2010  26777  Under25
4  2008  58809 Age25_34
5  2009  57239 Age25_34
6  2010  58558 Age25_34
7  2008  75677 Age35_44
8  2009  74900 Age35_44
9  2010  74136 Age35_44
10 2008  78537 Age45_54
11 2009  77460 Age45_54
12 2010  76266 Age45_54
13 2008  69009 Age55_64
14 2009  67586 Age55_64
15 2008  44402 Age65_74
16 2009  46147 Age65_74
17 2010  48595 Age65_74
18 2008  32747   Over75
19 2009  31272   Over75
20 2010  31638   Over75

> str(df)
'data.frame':   20 obs. of  3 variables:
 $ year  : int  2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 ...
 $ income: int  27907 25522 26777 58809 57239 58558 75677 74900 74136 78537 ...
 $ group : Factor w/ 7 levels "Age25_34","Age35_44",..: 7 7 7 1 1 1 2 2 2 3 ...

我想用cast来按组找到平均值.另外,我想从这个df创建一个宽的data.frame,第一列是年,下面的列是不同组的收入.例如

year     under25     Age25_34     Age35_44     Age45_54    ...
2008     27907        58809        75677        78537      ...
2009     25522        57239        74900        77460      ...
...

当我尝试演员时,我收到以下错误:

cast(df,income~group,mean)使用group作为值列.使用值参数进行强制转换以覆盖此选项错误[.data.frame(data,,variables,drop = FALSE):选中未定义的列

我对cast命令做错了什么？

如何将其转换为宽格式,如示例所示？

我的R版本信息如下所示.

> unlist(R.Version())
   platform                            arch                              os 
"x86_64-pc-mingw32"                  "x86_64"                       "mingw32" 

 system                          status                           major 
"x86_64, mingw32"                   ""                             "2" 

minor                            year                           month 
"13.1"                          "2011"                            "07" 

day                         svn rev                        language 
"08"                         "56322"                             "R" 
version.string 
"R version 2.13.1 (2011-07-08)" 

Answer 1

试试吧 cast

cast(df, year ~ group, mean, value = 'income')

  year Age25_34 Age35_44 Age45_54 Age55_64 Age65_74 Over75 Under25
1 2008    58809    75677    78537    69009    44402  32747   27907
2 2009    57239    74900    77460    67586    46147  31272   25522
3 2010    58558    74136    76266      NaN    48595  31638   26777

Answer 2

aggregate(cbind(year, income)~group, data=df, FUN=mean)
     group   year   income
1 Age25_34 2009.0 58202.00
2 Age35_44 2009.0 74904.33
3 Age45_54 2009.0 77421.00
4 Age55_64 2008.5 68297.50
5 Age65_74 2009.0 46381.33
6   Over75 2009.0 31885.67
7  Under25 2009.0 26735.33