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我有一个示例数据框“数据”，如下所示：

X          Y  Month   Year    income
2281205 228120  3   2011    1000
2281212 228121  9   2010    1100
2281213 228121  12  2010    900
2281214 228121  3   2011    9000
2281222 228122  6   2010    1111
2281223 228122  9   2010    3000
2281224 228122  12  2010    1889
2281225 228122  3   2011    778
2281243 228124  12  2010    1111
2281244 228124  3   2011    200
2281282 228128  9   2010    7889
2281283 228128  12  2010    2900
2281284 228128  3   2011    3400
2281302 228130  9   2010    1200
2281303 228130  12  2010    2000
2281304 228130  3   2011    1900
2281352 228135  9   2010    2300
2281353 228135  12  2010    1333
2281354 228135  3   2011    2340

我使用 ddply 计算每个Y的收入

x <- ddply(data, .(Y), summarize, freq=length(Y), tot=sum(income))
#Now, I also need to find out the X for each Y depending upon the following conditions: 
a. If Y consists of observations of months 9 (2010), 12 (2010), and 3 (2011), then the x corresponds to months 9(2010) i.e. for Y =228121 x=2281212
b. If Y consists of observations of month 6 (2010), 9 (2010), 12(2010) , and 3 (2011)  then the x corresponds to months 6 (2010) i.e. for Y =228122 x=2281222. 
c. If Y consists of observations of month 12 (2010), 3 (2011) then the x corresponds to months 12 (2010) i.e. for Y =228124 x=2281243. 
d. If Y consists of observations of month 12 (2010), 3 (2011) then the x corresponds to months 12 (2010) i.e. for Y =228124 x=2281243. 
e. If Y consists of only one observation then the x corresponds to month of that observation i.e. for Y =228120 x=2281205.

这里的要点是，如果我对每个 Y 有多个观察值，我选择对应于第 6 个月（2010 年）的 x（如果可用），但如果不可用，我选择接近 6 月（2010 年）的月份（例如 9（ 2010））。请注意，如果我只有一个观察结果，我将选择 x 作为该观察结果。

请建议如何将这些条件纳入 ddply。

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1 回答 1

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This solution assumes that earliest X value is selected as sugessted by @DWin. Month and Year variables are converted to date format and then earliest is selected as condition to select X.

library(zoo) #necessary for date manipulation
x <- ddply(data, .(Y), summarize, freq=length(Y), tot=sum(income),
 X=X[as.yearmon(paste(Month,Year,sep="/"),format="%m/%Y")==min(as.yearmon(paste(Month,Year,sep="/"),format="%m/%Y"))])

       Y freq   tot       X
1 228120    1  1000 2281205
2 228121    3 11000 2281212
3 228122    4  6778 2281222
4 228124    2  1311 2281243
5 228128    3 14189 2281282
6 228130    3  5100 2281302
7 228135    3  5973 2281352

EDIT - solution assuming that there could be values before 2010-06

library(zoo)
#new column containing dates made from Month and Year
data$Time<-as.Date(as.yearmon(paste(data$Month,data$Year,sep="/"),format="%m/%Y"))

#calculated difference between new date column and 2010-06
data$Time.dif<-abs(as.numeric(data$Time-as.Date("2010-06-01")))

#now selects X when Time.dif is smallest (0 in case of 2010-06)
x <- ddply(data, .(Y), summarize, freq=length(Y), tot=sum(income), 
           X=X[Time.dif==min(Time.dif)])
于 2013-01-02T20:47:47.843 回答