R help - Sep 2006 - R: Grouping columns in a data frame based on the values of a column

Perhaps using 'ave' and 'cut':

 df <- data.frame(x=runif(100, 0.1, 1),  y=rnorm(100, 0.2, 0.6))
 df$xcut<-cut(df$x, seq(0, 1, 0.1))
 df$z<-ave(df$y, df$xcut)
 df[order(df$x),]


Stefano

-----Messaggio originale-----
Da: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch]Per conto di
e.rapsomaniki at mail.cryst.bbk.ac.uk
Inviato: venerd? 15 settembre 2006 17.45
A: r-help at stat.math.ethz.ch
Oggetto: [R] Grouping columns in a data frame based on the values of a
column


Dear R users,

This is a trivial question, there might even be an R function for it, but I have
to do it many times and wonder if there is an efficient for it.


Suppose we have a data frame like this:
d <- data.frame(x=sample(seq(0.1:1, by=0.01), size=100, replace=TRUE),
y=rnorm(100, 0.2, 0.6))

and want to have the average of y for a given interval of x, for example
mean(y)[0>x>0.1]. Is there a simple way of doing this or I need to
improvise?

Thank you so much for any help
Eleni Rapsomaniki

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