How to access objects outside an R function

...I have a dataframe ('forexdata') of daily returns from the foreign exchange market for three currencies - British Pound (bp), Canadian
Dollar(cd),
Deustche Mark (dm) vis-a-vis the US Dollar and the Date Of
Trade(yymmdd).

For some dates the returns are missing (recorded as zero) as there
were no trades in that currency for that date. My task is to
substitute the missing or zero values with the next non-zero value.

Here is a function that will replace the zeros with the _last_  non-zero value (which is what you did in your solution). Note that it will produce
NAs if the _first_ value in a column is zero. Supply the data frame and a vector of column indices (in your case 3:5) to which you want to apply the
function. Hope this helps.

Jim


sub.last.value<-function(x.df,cols=1:dim(x.df)[2]) {
 nrows<-dim(x.df)[1]
 newcol<-vector("numeric",nrows)
 for(col in 1:length(cols)) {
  last.value<-NA
  for(row in 1:nrows) {
   if(x.df[row,cols[col]] > 0)
    newcol[row]<-last.value<-x.df[row,cols[col]]
   else newcol[row]<-last.value
  }
  x.df[cols[col]]<-newcol
 }
 return(x.df)
}


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