Example for ddply numerics problem

gistfile1.txt

library(plyr)

exampleData <- structure(list(movie = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L,
               1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "my_movie", class = "factor"),
                   normS1 = c(-0.00000514991529017386, 0.00000434044351014654,
                   0.000011374474150384, 0.00000791328447026715, 0.00000180037689006078,
                   -0.00000259589226008764, -0.000014779838190499, -0.0000025679794400867,
                   -0.0000208090073107025, -0.00000607103835020496, 0.00000872275625029448,
                   -0.00000428461787014465, -0.000000851341010028744, -0.00000168872561005701,
                   0.00000796911011026904, 0.00000787141524026574, 0.00000436835633014748,
                   0.00000336349481011355, -0.00000706194346023841, -0.00000343327686011591
                   )), .Names = c("movie", "normS1"), row.names = c(NA, 20L), class = "data.frame")

meanLast <- ddply(exampleData, .(movie), summarize,
  a="test",
  avgNormS1=1*mean(normS1)
)

meanFirst <- ddply(exampleData, .(movie), summarize,
  avgNormS1=1*mean(normS1),
  a="test"
)

meanLast
meanFirst