[R] Reading data from a dataframe

[David Winsemius]

"Alexander Ovodenko" <ovodenko at princeton.edu> wrote in
news:85e440020802090820n281dfffcwffee2807cb483a6e at mail.gmail.com: 

> Thanks for the replies to my prior question.  My problem is that R
> always says object not found when I enter a variable name into a
> command.  I converted a Stata file into an Rdata file by first
> loading the foreign package by entering
> 
> require(foreign)
> 
> Then I asked R to read the Stata file by entering
> 
> pol572a1<- read.dta("C:\\alex\\Graduate Coursework\\Pol
> 572\\pol572a1.dta") 

At this point you should type str(pol572a1) to make sure <everything> 
is the dataframe named pol572a1.

> 
> So now I can do a few things with the data, but I am only able to do
> so by entering
> 
> with(pol572a1,
> 
> before typing another command. So I enter the following for a
> scatter plot: with(pol572a1, plot(rgnpc, incmean))

If you wanted to avoid the with() function (but why would you?) you 
could have used:
 
plot(pol572a1$rgnpc, pol572a1$incmean)

> 
> When I run a simple linear regression, I enter the following:
> with(pol572a1, lm(incmean~rgnpc))

Which creates the model and immediately discards it, because no durable 
object was given the values:
 
> But when try to get a fitted line, I enter the following:
> with(pol572a1, lm( share.gnp)<-lm(incmean~rgnpc))  

That does not look particular sensible. Assuming that the goal was to 
create a model object named share.gnp, then try instead:

with(pol572a1, share.gnp.mdl <-lm(incmean~rgnpc) ) 

(My practice is to label my models, but it is not necessary.)

Then look at share.gnp.mdl with str() and you should see fitted.values. 
You could then plot() the fitted values and the observed values.


> But I get the
> following error message: Error in lm(share.gnp) <- lm(incmean ~
> rgnpc) : object "share.gnp" not found 
> 
> So what should I do to get R to read the dataframe in the ordinary
> way with the usual command?  

I cannot tell what you mean. It appears you already have the data in a 
dataframe.

> I am willing to scrap this dataframe
> and use the original Stata file to start over, as long as that
> resolves the problem. 
> 
> Thanks!
> 
> Alex
>