[R] Conditional variable assignment
dwinsemius at comcast.net
Tue Mar 16 21:04:50 CET 2010
On Mar 16, 2010, at 3:44 PM, Hosack, Michael wrote:
> Hi everyone,
> Once again I am stuck with a problem I can't seem to figure out. I
> suppose this learning curve levels off eventually, lol. I am
> learning on my own with absolutely no background in programming, so
> if I seem to request help a lot it's not because I am seeking others
> to do the work for me. I need to assign one of two arrival times to
> the 'ARRIVE' variable of my dataframe, and I want a value assigned
> only to the first element of each 'MM' by 'DD' variable grouping.
> The value used (either 0700 or 1430) will be conditional on the
> value in the 'TOD' variable, such that if 'TOD' == 1,
> 'ARRIVE'<-0700, and if 'TOD'==2, 'ARRIVE'<-1430. I want the
> remaining three 'MM' by 'DD' values for each unique grouping to
> remain "NA" for now, because I intend to calculate them later. I
> have tried ifelse statements with ddply, for loops, etc. to no
> avail. Any help would be greatly appreciated.
dfrm[!duplicated(paste(dfrm$MM, dfrm$DD)), "ARRIVE"] <- "0700"
dfrm$ARRIVE[dfrm$ARRIVE == "0700" & dfrm$TOD=="2"] <- "1430"
David Winsemius, MD
West Hartford, CT
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