On Aug 9, 2010, at 10:11 AM, moleps wrote:

ldply doesnt need a grouping variable as far as I understand the command..

There is one further improvement to consider. When I tried using dlply to tackle a problem on which I had been bashing my head for the last three days and it gave just the results I had been looking for, I also noticed that the dlply function returns the grouping variable levels in an attribute, "split_labels", which could be unlisted to use as an argument to the rep() call I suggested earlier:

dfdl$group=rep(unlist(attr(dl, "split_labels")), each=4)

That might make the results more self-documenting in situations where the grouping levels were more involved than 0:2.

(Now, if I can get rms::Predict to behave as nicely with the plyr functions as did rms::cph, I will be home free.)
--
David.

"Description

For each element of a list, apply function then combine results into a data frame

Usage

ldply(.data, .fun = NULL, ..., .progress = "none")"


regards,

M


On 9. aug. 2010, at 15.33, David Winsemius wrote:


On Aug 9, 2010, at 7:51 AM, moleps wrote:

Dear all,

I´m having trouble getting a list of regression variables back into a dataframe.

mydf <- data.frame(x1=rnorm(100), x2=rnorm(100), x3=rnorm(100))

mydf$fac<-factor(sample((0:2),replace=T,100))

mydf$y<- mydf$x1+0.01+mydf$x2*3-mydf$x3*19+rnorm(100)

dlply(mydf,.(fac),function(df) lm(y~x1+x2+x3,data=df))->dl

here I´d like to use

ldply(dl,coef(summary)) or something similar but I cant figure it out...

dfdl <- ldply(dl, function(x) coef(summary(x)) )

Doesn't create a grouping variable, so:

dfdl$group=rep(0:2, each=4)


David Winsemius, MD
West Hartford, CT



David Winsemius, MD
West Hartford, CT

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