R help - Apr 2005 - "chronological" ordering of factor in lm() and plot()

I am trying to do some basic regression and ANOVA on cycle times (numeric
vectors) across weekdays (character vector), where I have simply labelled my
days as:
days<- c("mon","tue","wed"...etc).
(NOTE: There are actually multiple instances of each day, and the data is
read-in from a .dat file.)

I have no trouble at all with the actual number crunching, It is the
"proper" ordering of the factor that I am asking about. R first
alphabetizes
it("fri","mon","thu"...) before doing the work of
lm(), aov() and especially
plot().

I have tried as.ordered(factor( )), but that doesn't do anything.
If I re-assign levels() in the way that I want, that just renames the the
levels of the factor but does not reorder it internally.
I've looked at chron(), but that seems to entail using a numeric vector
instead of a character vector.

How can I get it to "properly" (chronologically) order the factor. (In
some
ways I'm thinking that all I can do is:
days<- c("a.mon","b.tues","c.wed"...etc)

Thanks for all that you can do
Eric Jennings
matheric at u.washington.edu
matheric at myuw.net

On 4/16/05, Eric C. Jennings <matheric at myuw.net>
wrote:
> I am trying to do some basic regression and ANOVA on cycle times (numeric
> vectors) across weekdays (character vector), where I have simply labelled
my
> days as:
> days<- c("mon","tue","wed"...etc).
> (NOTE: There are actually multiple instances of each day, and the data is
> read-in from a .dat file.)
> 
> I have no trouble at all with the actual number crunching, It is the
> "proper" ordering of the factor that I am asking about. R first
alphabetizes
> it("fri","mon","thu"...) before doing the
work of lm(), aov() and especially
> plot().
> 
> I have tried as.ordered(factor( )), but that doesn't do anything.
> If I re-assign levels() in the way that I want, that just renames the the
> levels of the factor but does not reorder it internally.
> I've looked at chron(), but that seems to entail using a numeric vector
> instead of a character vector.
> 
> How can I get it to "properly" (chronologically) order the
factor. (In some
> ways I'm thinking that all I can do is:
> days<- c("a.mon","b.tues","c.wed"...etc)
> 
Try this:
> f.wrong <- factor(c("mon", "fri", "mon",
"fri"))
> f.wrong
[1] mon fri mon fri
Levels: fri mon
> f.right <- factor(f.wrong, levels = c("mon", "fri"))
> f.right
[1] mon fri mon fri
Levels: mon fri

First put
> day.names <- c("sun", "mon", "tue",
"wed", "thu", "fri", "sat")
then
> days <- factor(as.character(days), levels = day.names)
will ensure the ordering you want.

Bill Venables.

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Eric C. Jennings
Sent: Saturday, 16 April 2005 2:29 PM
To: R-help
Subject: [R] "chronological" ordering of factor in lm() and plot()


I am trying to do some basic regression and ANOVA on cycle times
(numeric
vectors) across weekdays (character vector), where I have simply
labelled my
days as:
days<- c("mon","tue","wed"...etc).
(NOTE: There are actually multiple instances of each day, and the data
is
read-in from a .dat file.)

I have no trouble at all with the actual number crunching, It is the
"proper" ordering of the factor that I am asking about. R first
alphabetizes
it("fri","mon","thu"...) before doing the work of
lm(), aov() and
especially
plot().

I have tried as.ordered(factor( )), but that doesn't do anything.
If I re-assign levels() in the way that I want, that just renames the
the
levels of the factor but does not reorder it internally.
I've looked at chron(), but that seems to entail using a numeric vector
instead of a character vector.

How can I get it to "properly" (chronologically) order the factor. (In
some
ways I'm thinking that all I can do is:
days<- c("a.mon","b.tues","c.wed"...etc)

Thanks for all that you can do
Eric Jennings
matheric at u.washington.edu
matheric at myuw.net

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