I apologize about cross posting but my question keeps bouncing back from the list How come pct doesn't work in this ddply call? I am trying to get a percent of 'TotalCount' by SampleDate and Age library(plyr) b <- structure(list(SampleDate = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "5/8/1996", class = "factor"), TotalCount = c(1L, 2L, 1L, 1L, 4L, 3L, 1L, 10L, 3L), ForkLength = c(61L, 22L, NA, NA, 72L, 34L, 100L, 23L, 25L), TotalSalvage = c(12L, 24L, 12L, 12L, 17L, 23L, 31L, 12L, 15L), Age = c(1L, 0L, NA, NA, 1L, 0L, 1L, 0L, 0L)), .Names = c("SampleDate", "TotalCount", "ForkLength", "TotalSalvage", "Age"), class = "data.frame", row.names = c(NA, -9L)) b ddply(b,.(SampleDate,Age),summarise,salvage=sum(TotalSalvage),pct=TotalCount/sum(TotalCount)) Error: expecting result of length one, got : 4 #Computing TotalCount inside ddply works but the pct seems wrong... ddply(b,.(SampleDate,Age),summarise,salvage=sum(TotalSalvage),Count=sum(TotalCount),pct=Count/sum(Count)) [[alternative HTML version deleted]]
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