CODEWITHSUNDEEP
rdataframe
ABC
ABC

Reputation: 341

better form for mean of subset data

i have a data set :

    X     Y
   20     12
   24     11
   12      7
   10      2
   41     24
   13      9
   50     17
    4     12
   17     12
   35     19

Now i have to find the mean of Y when 20 < X < 50.

My attempt:

     data <- data.frame(X=c(20,24,12,10,41,13,50,4,17,35),
                        Y=c(12,11,7,2,24,9,17,12,12,19))
     sub <- subset(data,X>20 & X<50)
     mean(sub$Y)

Is there any direct way to find the mean of Y when 20< X<50 without modifying the original data frame ,ie, without subset it?

Upvotes: 0

Views: 153

Answers (2)

agstudy
agstudy

Reputation: 121578

Or, using data.table for its syntactic sugar:

 library(data.table)
 DT <- data.table(data)
 DT[X>20 & X <50,mean(Y)]
 [1] 18

Upvotes: 4

Jake Burkhead
Jake Burkhead

Reputation: 6535

Not sure what you mean by "without subset it". At some point you are going to have to subset the data in some way since you are looking for the mean of a subset of the data. If you mean "don't call the subset function and save another copy of the data" you can just do 

mean(data$Y[data$X > 20 & data$X < 50])
# [1] 18

Upvotes: 7

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