I'm so sorry... I was very busy but I found a solution with an extra line sum(x[[col]])
data_summary_session2 <- function(data = dfdata_session2, varname = Nombre.de.contacts, groupnames = c(Odeur, Type.de.test)){
require(plyr)
summary_func <- function(x, col){
c(mean = mean(x[[col]], na.rm=TRUE),
sd = sd(x[[col]], na.rm=TRUE),
sum = sum(x[[col]], na.rm = TRUE))
}
data_sum<-ddply(data, groupnames, .fun=summary_func,
varname)
data_sum <- rename(data_sum, c("mean" = varname))
return(data_sum)
}
Thanks a lot for your help