R：应用，自定义函数和数据框名称

Question

I have a data frame Indices containing various names which correspond to data frames ( ie a name "Index 1" has a corresponding data frame Index 1 ).

Now I want to run my custom function calcScores over all data frames and add several columns to that data frame. Since I'm not in the global environment I return that "new" data frame and want to assign it back to the original variable Index 1 , so Index 1 now has the new data frame with the added columns.

Here's my code (no chance I can make this 100% reproducible since all data is very custom but I hope you understand my question).

# Here the unique Index names are derived and stored
# Problem is the index names are stored as "Index 1", "Index 2" etc.
# Thats why I have to adjust These #titles and create individual data Frames
Indices <- unique(df[1])
apply(unique(df[1]), 1, function(x){
    assign(gsub(" ","",x,fixed=TRUE), subset(df,ticker==x), envir = .GlobalEnv)
})

calcRollingAverage <- function(Parameter, LookbackWindow){
    Output <- rollapply(Parameter, LookbackWindow, mean, fill=NA, partial=FALSE,
                        align="right")
}

calcScores<-function(Index, LookbackWindow){
    Index$PE_Avg = calcRollingAverage(Index$PE_Ratio, LookbackWindow)
    Index$PE_DIV_Avg = Index$PE_Ratio/Index$PE_Avg
    Index$PE_Score = cut(Index$PE_DIV_Avg, breaks=PE_Breaks, labels=Grades)

    return(Index)
}

apply(Indices,1,function(x) assign(gsub(" ","",x,fixed=TRUE), calcScores(get(gsub(" ","",x,fixed=TRUE)),lookback_window)))

I guess my problems are in the apply and with the whole get , assign and gsub story. The scoping is here obviously the issue... At the moment apply gives the following error:

Error: unexpected symbol in:
"apply(Indices,1,function(x) assign(gsub(" ","",x,fixed=TRUE), calcScores(get(gsub(" ","",x,fixed=TRUE)),lookback_window))
apply"

Answer 1

Ok solved it...sorry for the post. That is the solution: envir = .GlobalEnv

apply(Indices,1,function(x) assign(gsub(" ","",x,fixed=TRUE), calcScores(get(gsub(" ","",x,fixed=TRUE)),lookback_window),envir = .GlobalEnv))

Answer 2

Why don't you just use a for loop, which would help with the scoping problems ? Something like this :

mydf1 <- data.frame(x=1:3, y=2:4)
mydf2 <- data.frame(x=3:5, y=4:6)

indices <- c("mydf1","mydf2")

for (dfname in indices) {
    result <- get(dfname)
    result$z <- result$x+ result$y
    assign(dfname, result)
}

Answer 3

Looks like you want to split your data by ticker and apply a function on each splitted element.

This is a job for by or ddply in plyr package.

by(df,df$ticker,FUN=calcScores,LookbackWindow=lookback_window)