Hi all, i have a little problem, and i think it is really simple to solve, but i dont know exactly how to. here is the "challange": i have a data.frame with n colum, i have to group 2 of them and calculate the mean value of the 3. one. so far so good, that was easy - i used aggregate function to do this: group<-aggregate(x[,1],list(x[,2],x[,3]),mean) and now i have to copy the calculated mean value to every row of the date.frame (in a new column in the dataframe), ofcourse by copying should be the value adequate to the group it will be great if someone can help me thanx in advance! -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324240.html Sent from the R help mailing list archive at Nabble.com.
Hi,
I think ave() might do what you want:
df <- data.frame(a=rep(c("this","that"),5), b1=rnorm(10),
b2=rnorm(10))
ave(df[,2], df[,1], FUN=mean)
For all columns, you could do that:
d <- lapply(df[,2:3], FUN=function(x)ave(x,df[,1],FUN=mean))
df2 <- cbind(df, d)
HTH,
Ivan
Le 2/25/2011 12:11, zem a ?crit :> Hi all,
>
> i have a little problem, and i think it is really simple to solve, but i
> dont know exactly how to.
> here is the "challange":
> i have a data.frame with n colum, i have to group 2 of them and calculate
> the mean value of the 3. one. so far so good, that was easy - i used
> aggregate function to do this:
> group<-aggregate(x[,1],list(x[,2],x[,3]),mean)
> and now i have to copy the calculated mean value to every row of the
> date.frame (in a new column in the dataframe), ofcourse by copying should
be
> the value adequate to the group
>
> it will be great if someone can help me
> thanx in advance!
--
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de
**********
http://www.for771.uni-bonn.de
http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php
Hi Ivan, thanks for your replay! but the problem is there that the dataframe has 20000 rows and ca. 2000 groups, but i dont have the column with the groupnames, because the groups are depending on 2 onother columns ... any other idea or i didnt understand waht are you posted ... :( -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324327.html Sent from the R help mailing list archive at Nabble.com.
10x i solved it ... mein problem was that i had 2 column by them i have to group, i just "pasted" the values together so that at the end i have one column to group and then was easy ... here is the script that i used: http://tolstoy.newcastle.edu.au/R/help/06/07/30184.html Ivan thanks for the help too :) -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324469.html Sent from the R help mailing list archive at Nabble.com.
Yeah, you are right i want to post an short example what i want to do .. and in the meantime i solved the problem ... but here is: i have something like this dataframe: c1<-c(1,2,3,2,2,3,1,2,2,2) c2<-c(5,6,7,7,5,7,5,7,6,6) c3<-rnorm(10) x<-cbind(c1,c2,c3)> xc1 c2 c3 [1,] 1 5 0.08279036 [2,] 2 6 0.59135988 [3,] 3 7 1.45520468 [4,] 2 7 -1.70094640 [5,] 2 5 0.13065228 [6,] 3 7 -1.12080980 [7,] 1 5 0.42779354 [8,] 2 7 -1.53111972 [9,] 2 6 0.29299987 [10,] 2 6 -0.01602095 #whith aggregate i receive this:>aggregate(x[,3],list(x[,1],x[,2]),mean)Group.1 Group.2 x 1 1 5 0.2552920 2 2 5 0.1306523 3 2 6 0.2894463 4 2 7 -1.6160331 5 3 7 0.1671974 and the problem was that i was grouping by 2 columns, so i couldn't copy the result to x. the solution was i made another column with paste(x[,1],x[,2],sep="_") and then i used the solution from this link: http://tolstoy.newcastle.edu.au/R/help/06/07/30184.html so i solved my problem Ivan, many thanks for your support and quik responses! :) -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324608.html Sent from the R help mailing list archive at Nabble.com.
hi guys, many many thanks for all the solutions! :-D they are working great! i have another "little" question: i would like to save these groups in a new column with serial number like the solution from David, but wit integer values: 1,2,3... i do this allready but with my 1. solution and there is to much temp-data, that i dont realy nead ... if you have any idea, that'll be really great! thanks a lot ! -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3325199.html Sent from the R help mailing list archive at Nabble.com.