[R] Just 2 more questions - for now!

[Mark Difford]

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]]
> 
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> 

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