Re: [R] Just 2 more questions - for now!

From: Mark Difford <mark_difford_at_yahoo.co.uk>
Date: Thu, 24 Jul 2008 05:16:47 -0700 (PDT)

Hi Robin,

>> I ... can't get lm to work despite reading the help. I can get it to work
>> with a single 
>> explanatory variable, EG model <- lm(data$admissions~data$maxitemp)

I'll answer just the second of your questions. Advice: don't just read the help file, look at the examples and run them; look at how the calls are made. lm() and many other programs use (or can use) the ?formula interface, so learn how to use it. For your "example," rather do

##
EGModel <- lm(admissions ~ maxitemp, data = data)

where data is your data set (to avoid confusion call it something else, e.g. mydata). To add another variable/predictor, which should be in your data frame (for simplicity) called data, simply do

EGModel <- lm(admissions ~ maxitemp+another.var, data = data)

If your maxitemp(s) occur at different sites, then you might be interested in a nested model

EGModel1 <- lm(admissions ~ site/maxitemp - 1, data = data) EGModel2 <- lm(admissions ~ site*maxitemp, data = data) ## alt. parameterization
anova(EGModel1, EGModel2)
anova(EGModel, EGModel1, EGModel2, test="Chi")

This shows part of the power of using the formula interface.

HTH, Mark.

Williams, Robin wrote:
>
> Hi all,
> Thanks for the help with my previous post.
> I have just two more questions for the minute.
> I think I said in a previous post that I like to use the terminal,
> i.e. run rterm.exe. On exiting the terminal, I am asked if I want to
> save the workspace. If I hit y (yes), the workspace is just saved as
> .rdata in my working directory, does anyone know how I can name it
> directly from the terminal?
> More importantly, I can't then open this file from the terminal.
> Obviously loading the file from windows explorer brings up the GUI.
> Anyone know the command I need? All I can think of doing is adding
> rterm.exe to my path and running it from the command prompt (adding the
> file as an argument to my command), but surely there is an easy way to
> do this from R? Of course I would like to have the terminal open and
> open and close various workspaces in one session, without wanting to
> restart R all the time.
>
> Finally, I rather embarrasingly can't get lm to work despite reading
> the help. I can get it to work with a single explanatory variable, EG
> model <- lm(data$admissions~data$maxitemp)
> but how to include a second explanatory variable (minitemp)? I keep
> getting errors. Surely I don't need to use
> c(data$maxitemp,data$minitemp) etc?
>
> All help greatly appreciated - I am getting there slowly!
>
>
> Robin Williams
> Met Office summer intern - Health Forecasting
> robin.williams_at_metoffice.gov.uk
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help_at_r-project.org mailing list
>
https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

-- 
View this message in context: http://www.nabble.com/Just-2-more-questions---for-now%21-tp18629686p18630709.html
Sent from the R help mailing list archive at Nabble.com.

______________________________________________
R-help_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Received on Thu 24 Jul 2008 - 12:26:14 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Thu 24 Jul 2008 - 13:32:27 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.

list of date sections of archive