William Revelle wrote:
Dear list friends
I fail to understand how to find means for multiple groups using the
by() function. Help would be appreciated. Thanks.
Bill
x <- runif(20,0,10)
group <- rep(c("A","B"),10)
df <-data.frame(x,group)
#df #show the data
rm(x,group)
attach(df)
sd(x) # sd is defined
mean(x) #so is mean
by(x,group,sd) #this works for both groups
by(x,group,mean) #this does not
produces this output:
x <- runif(20,0,10)
group <- rep(c("A","B"),10)
df <-data.frame(x,group)
#df #show the data
rm(x,group)
attach(df)
sd(x) # sd is defined
[1] 2.952699
mean(x) #so is mean
[1] 5.026441
by(x,group,sd) #this works for both groups
INDICES: A
[1] 2.813504
------------------------------------------------------------------------------------------------------------
INDICES: B
[1] 3.236663
by(x,group,mean) #this does not
Error in FUN(X[[as.integer(1)]], ...) : couldn't find function "FUN"
I am using a Mac OS 10.3.4 running R 1.9.1
Hi Bill,
Works for me. Do you have a local "mean" defined? Try rm(mean) and re-try.
> R.version
_
platform i386-pc-mingw32
arch i386
os mingw32
system i386, mingw32
status
major 1
minor 9.1
year 2004
month 06
day 21
language R
--sundar
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