Two Noobie questions

On Jan 6, 2009, at 1:50 PM, AllenL wrote:

1. I have a list of lm (linear model) objects. Is it possible to  
select,
through subscripts, a particular element (say, the intercept) from  
all the
models? I've tried something like this:

?coef
if your list of models is ml, then perhaps something like this  
partially tested idea:

lapply(ml, function(x) coef(x)[1] )

This is what I get using that formulation an available logistic model:

 > coef(lr.TC_HDL_BMI)[1]

Intercept
-6.132448

List[[1:length(list)]][1]
All members of the list are similar. My goal is to have a list of the
intercepts and lists of other estimated parameters. Is it better to  
convert
to a matrix? How to do this?

2. Connected to this, how do I convert from a list back to a vector?  
This
problem arose from using "split" to split a vector by a factor, then
selecting a subset of this (ie. length>10), leaving me with subset  
list of
my original. Unsplit(newList, factor) doesn't work, presumably due  
to my
removal of some values. Thoughts?

?unlist

 > ll <- list(1,2,3,4)
 > ll

[[1]]
[1] 1

[[2]]
[1] 2

[[3]]
[1] 3

[[4]]
[1] 4

 > unlist(ll)

[1] 1 2 3 4

 > str(unlist(ll))

  num [1:4] 1 2 3 4

 > is.vector(unlist(ll))

[1] TRUE

-- 
David Winsemius

Thanks!
-Allen



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