On Sep 21, 2010, at 6:52 PM, Simon Kiss wrote:
hello, can someone tell me how to generate the means for a data
frame that looks like this? My data frame has many more variables,
but I won't bother you with those; these are the one's that I'm
interested in.
Needless to say, z is the variable in which I'm interested. I'd like
to find out the mean score of z for NDP managers, Conservative
managers and Liberal managers and then for a few other configurations.
Ive played around with aggregate, tapply and by, but I can't get it
to work.
Cordially,
Simon Kiss
mydata=data.frame(cbind(x,y,z))
How about testing your code? That throws an error;
mydata$x=as.factor(sample(c("labourers", "salaried", "managers"),
size=300, replace=TRUE))
mydata$y=as.factor(sample(c("NDP", "Green", "Liberal",
"Conservative"), size=300, replace=TRUE))
mydata$z=as.numeric(sample(1:4, size=300, replace=TRUE))
Try instead:
mydata <-data.frame(
x=as.factor(sample(c("labourers", "salaried", "managers"), size=300,
replace=TRUE)),
y=as.factor(sample(c("NDP", "Green", "Liberal", "Conservative"),
size=300, replace=TRUE)), z=as.numeric(sample(1:4, size=300,
replace=TRUE))
)
> str(mydata)
'data.frame': 300 obs. of 3 variables:
$ x: Factor w/ 3 levels "labourers","managers",..: 2 2 1 1 1 2 1 3 2
3 ...
$ y: Factor w/ 4 levels "Conservative",..: 3 2 3 2 4 1 1 3 3 4 ...
$ z: num 3 3 2 4 4 1 1 3 4 1 ...
Then with a valid object ...
> with( subset(mydata, x == "managers"),
tapply(z, y, mean) )
Conservative Green Liberal NDP
2.161290 2.333333 2.615385 2.333333
*********************************
Simon J. Kiss, PhD
Assistant Professor, Wilfrid Laurier University
223 Grand River Hall, 171 Colborne Street
Brantford, Ontario, Canada
N3T 2C9
Cell: +1 519 761 7606
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
