Dear all I have a dataframe containing hourly data of 3 parameters. I would like to create a dataframe containg daily mean values of these parameters. Additionally I want to keep information about time of measurement ("year","month","day"). With the function tapply I can average over a column of the dataframe. I can repeat the function 2 time and merge the vectors. In this way I obtain my new dataframe (see below).If I want to add the column day, month and year I can repeat tapply other three time. This system works.
Question: is there a function that average in a single step over the 3 columns? Thanks a lot for your answer! Regards Mike Campana #### read the data setwd("c:/R") data <- NULL data <- as.data.frame(read.table(file="Montreal.txt",header=F,skip=15)) colnames(data) <-c("year","month","day","hour","min","temp","press","ozone") ### create mean value temp_daily <- tapply(data$temp,data$year*10000+data$month*100+data$day,FUN=mean) press_daily <- tapply(data$press,data$year*10000+data$month*100+data$day,FUN=mean) ozone_daily <- tapply(data$ozone,data$year*10000+data$month*100+data$day,FUN=mean) ### merge the data newdata <- as.data.frame (cbind(temp_daily,temp_daily,temp_daily)) --- --- --- --- --- ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html