placing mean,total and max together in a table in r

Question

I have some simple commands looking into totals, means and maximums of a variable whilst another variable is an assigned value:

sum(data[data$var1==1,]$var2)
mea         


        

Answer 1

You need to use cbind for that.

cbind(sum(data[data$var1==1,]$var2),mean(data[data$var1==1,]$var2),max(data[data$var1==1,]$var2))

Example using mtcars data

mydata<-mtcars  
  l<-cbind(sum(mydata[mydata$cyl==4,]$mpg),mean(mydata[mydata$cyl==4,]$mpg),max(mydata[mydata$cyl==4,]$mpg))
l<-data.frame(l)
names(l)<-c("sum","mean","max")
> l
    sum     mean  max
1 293.3 26.66364 33.9

There is a ddply function from plyr package that does all for each categories of var1 (here cyl)

library(plyr)
ddply(mydata,.(cyl),summarize, sum=sum(mpg),mean=mean(mpg), max=max(mpg))

 ddply(mydata,.(cyl),summarize, sum=sum(mpg),mean=mean(mpg), max=max(mpg))
  cyl   sum     mean  max
1   4 293.3 26.66364 33.9
2   6 138.2 19.74286 21.4
3   8 211.4 15.10000 19.2