[R] R loop within a loop

[saliluna]

I've also tried to make the function work for one particular group, then
apply the same function to the whole data frame with all groups using by()
or lapply() as follow. But I'm still receiving error messages. Could someone
please explain what is happening here?

dfdfdf <- function(localdata){
ordering <- c()
ordering[1] <- ifelse(localdata[1, ]$prev_event == 0, localdata$event,
localdata[1, ]$prev_event)
for (i in 2:nrow(localdata)){
ordering[i] <- localdata[localdata$prev_event == ordering[i-1], ]$event}
}

by(mydata, INDICES = mydata$group, FUN = dfdfdf)
lapply(mydata, FUN = dfdfdf)

Error in ordering[i] <- localdata[localdata$prev_event == ordering[i -  : 
  replacement has length zero
In addition: Warning message:
In ordering[i] <- localdata[localdata$prev_event == ordering[i -  :
  number of items to replace is not a multiple of replacement length


Thanks a lot!!



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