1. I need to make it an ordered factor in order to run ordered logit. I could
keep it unordered and run a multinomial logit, but that's beyond my capacity as
a new social science grad student (can't interpret it)
2. this is the sample code I tried before running it on my data.
> x <- c("favor","oppose","havent thought","favor","oppose")
> xf <- factor(x)
> attributes(xf)
$levels
[1] "favor" "havent thought" "oppose"
$class
[1] "factor"
> levels (xf)
[1] "favor" "havent thought" "oppose"
> xo <- ordered(x, levels=c("oppose","havent thought","favor"))
> attributes(xo)
$levels
[1] "oppose" "havent thought" "favor"
$class
[1] "ordered" "factor"
> levels(xo)
[1] "oppose" "havent thought" "favor"
> cbind(x,xf,xo)
x xf xo
[1,] "favor" "1" "3"
[2,] "oppose" "3" "1"
[3,] "havent thought" "2" "2"
[4,] "favor" "1" "3"
[5,] "oppose" "3" "1"
> table(x,xf)
xf
x favor havent thought oppose
favor 2 0 0
havent thought 0 1 0
oppose 0 0 2
> table(x,xo)
xo
x oppose havent thought favor
favor 0 0 2
havent thought 0 1 0
oppose 2 0 0
3. This worked fine in my made up scenario, but not when I played with the real
data.
4.This is a large data set, by my standards at least, but I've included it.
Thanks for all the help....I'll continue to play with it.
________________________________
From: David Winsemius [mailto:dwinsem...@comcast.net]
Sent: Thu 2/4/2010 9:26 AM
To: oli...@gmx.de
Cc: Mathew, Abraham T; r-help@r-project.org
Subject: Re: [R] Changing an unordered factor into an ordered factor
On Feb 4, 2010, at 5:58 AM, Oliver Gondring wrote:
> Hi Mathew,
>
>> I'm trying to change an unordered factor into an ordered factor:
>> Help
>
>
> it's all about reordering the factor levels, right?
It's hard to tell. You could be correct, but the OP never described
his reasons for wanting "ordered" factors. The page you offer below
only describes the "ordering" or "releveling" of the levels in
_unordered_ factors and does not describe creating or working with
ordered factors which are of a different class.
Ordered factor have additional methods
> x <- factor(sample(c("Oppose", "Haven't thought much about this",
"Favor"), 10, replace=TRUE) )
> x
[1] Oppose Favor
Oppose
[4] Favor Haven't thought much about this
Oppose
[7] Oppose Oppose
Oppose
[10] Oppose
Levels: Favor Haven't thought much about this Oppose
> ox <- factor(x, levels=c("Haven't thought much about
this","Oppose", "Favor"), ordered=TRUE)
> ox
[1] Oppose Favor
Oppose
[4] Favor Haven't thought much about this
Oppose
[7] Oppose Oppose
Oppose
[10] Oppose
Levels: Haven't thought much about this < Oppose < Favor # Note the
difference here.
> ox[1] < ox[3]
[1] FALSE # the < operator is meaningful here
> x[1] < x[3]
[1] NA
Warning message:
In Ops.factor(x[1], x[3]) : < not meaningful for factors
>
>
> Have a look at this one:
> http://rwiki.sciviews.org/doku.php?id=tips:data-factors:factors
>
> The third textbox on the page (search for the string: "Reorder factor
> levels") provides a piece of sample code for the task. Should be
> easy to
> adapt it to your problem.
>
> Oliver
>
> P.S.: Maybe it's not a bad idea to provide a more readable
> transformation of your code next time. What about replacing the whole
> 'V961327' thing by 'x' for example?
>
And maybe some sample data as well?
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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