將多個參數組合到多個數據幀的循環中

Question

我有多個不同行長度的數據幀。我想將它們組合成一個數據框，但在我這樣做之前，我想要在數據框上循環多個功能。我的主要問題是我不知道如何執行多個數據框的多個功能。

我有文件名列表：對於例如dataframes名單是：

stationlist <- c("StationAlpha","StationBeta") 

這兩個例子dataframes：

StationAlpha<- 
structure(list(YEAR = c(1979L, 1979L, 1979L, 1979L, 1979L), MONTH = 8:12, 
X1 = c(0, 5.6, 7.6, 0, 11), X2 = c(0, 2.6, 4.7, 0.4, 0), 
X3 = c(0, 0, 0, 0, 0)), .Names = c("YEAR", "MONTH", "X1", 
"X2", "X3"), row.names = c(NA, 5L), class = "data.frame") ### Example file 1 

StationBeta<- 
structure(list(YEAR = c(2001L, 2001L, 2001L, 2001L, 2001L), MONTH = 4:8, 
X1 = c(2.5, 3.3, 18, 13.5, 0), X2 = c(0.9, 10, 0, 1.5, 0), 
X3 = c(9, 0, 0, 7.5, 3.7)), .Names = c("YEAR", "MONTH", "X1", 
"X2", "X3"), row.names = c(NA, 5L), class = "data.frame") ### Example file 2 

的樣子：

YEAR|MONTH | X1 |X2 |X3 |etc. 
... 
2001| 4 |2.5 |0.9 |9.0 |... 
2001| 5 |3.3 |10.0 |0.0 |... 
2001| 6 |18.0 |0.0 |0.0 |... 
2001| 7 |13.5 |1.5 |7.5 |... 
2001| 8 |0.0 |0.0 |3.7 |... 
....etc. 

這些是我想要在所有數據幀上執行的功能：

test<-melt(StationAlpha, id=c("YEAR","MONTH"), variable.name = "day") #combine day columns to one big column 
test$day<-gsub("X","",test$day);test$day<-as.numeric(test$day) # change days to numeric value 
test$date <- as.Date(with(test, paste(YEAR, MONTH, day,sep="-")), "%Y-%m-%d") # make date from year,month,day 

# make a data frame with dates and day of year 
Ex.dates<-seq(as.Date("1940/01/01"), as.Date("2015/12/31"), "days") # vector with dates 
df.append <-data.frame(Ex.dates); df.append$DayofYear<-df.append$Ex.dates; df.append$DayofYear<-strftime(df.append$DayofYear, format = "%j") 
df.append$DayofYear<-as.numeric(df.append$DayofYear); names(df.append)<-c("date","DayOfYear") 

# Combine both dataframes on column "date" and leaves out duplicates but keep empty rows # Method 2 
df <- merge(df.append,test,by.x='date',by.y='date',all.x=T,all.y=T) 
df$value<- ifelse(df$value < 0, -99, df$value) # replace negative values with -99 

這是我想的dataframes合併成一個看起來像：

date  |DayOfYear | YEAR |MONTH|day|StationAlpha|StationBeta|StationEtc 
... 
2001-05-01| 121 |2005 |5 |1 |5.6   |3.3  |5.1 
2001-05-02| 122 |2005 |5 |2 |2.6   |10.0  |7.3 
2001-05-03| 123 |2005 |5 |3 |0.0   |0.0  |0.0 
2001-05-04| 124 |2005 |5 |4 |NA   |NA   |2.1 
2001-05-05| 125 |2005 |5 |5 |NA   |NA   |0.0 
....etc. 

你能告訴我或暗示我，我怎麼會用一個有關這些例子dataframes循環？或者拉普利/薩普利，如果這給出了相同的結果？

Answer 1

如何將功能應用到每個數據幀：

1）列出dataframes

stationlist<-mget(ls(pattern="X9")) 
# just made a list of data frames starting with "X9" as this is characteristic for my type dataframe names, but for the example the following is sufficient: 
stationlist<-list(StationAlpha,StationBeta) 

2）使用for循環，執行每個功能

my.melt <- function(x){ 
    x <- melt(x, id.vars=c("YEAR","MONTH"), 
      variable.name="day") 
    x 
} # melt function in order to be able to melt the days of the month 

for (i in 1:length(stationlist)){ 
    stationlist[[i]] <- my.melt(stationlist[[i]]) 
} # melt the days of the month 

for (i in 1:length(kenyastationlist)){ 
    stationlist[[i]]$day <- gsub("X","",stationlist[[i]]$day) 
} #remove the X from the stringvalue, before turning it into a number of day 

等適用於循環其他功能a脹。

3）合併列表中的所有dataframes到一個，同時保持與獨特COLUMNNAMES列：

Combined_df<- Reduce(function(x, y) merge(x, y, all=TRUE),stationlist) # combine all into one dataframe