Hi Michael,
The trick here is that r['...'] expects the ... to be an object name,
rather than a statement to be executed. The brackets following the
name 'r' is shorthand for 'obtain the object named ... from r', which
can also be expressed as,
r.get('...')
RPy provides a similar syntax for executing arbitrary r code:
r('...']
This is shorthand for 'execute r as a function on the following code
snippet', or
r.eval(r.parse('...'))
So, either of the following expressions will accomplish the same thing:
r['pwr.p.test'](h=0.2,power=0.95,sig_level=0.05) # get the R object
named 'pwr.p.test' and call it as a function
or
r('pwr.p.test(h=0.2,power=0.95,sig.level=0.05)') # execute this R
code.
-Greg
On Jun 19, 2007, at 11:32AM , Michael Grollman wrote:
>
> Greg / Kevin,
>
> Thanks, each of the solution's works. Much appreciated.
>
> This one appears to need a minor tweak, from:
>
> import rpy
> rpy.r.library("pwr")
> rpy.r.pwr_p_test(h=0.2,power=0.95,sig.level=0.05)
>
> to
>
> ... sig_level=0.05...
>
> Which makes sense, given Greg's explanation provided about the dot
> versus
> the underscore.
>
> This answers my main question. Thank you! I will drop this side
> issue
> below out there, as it is what got me stuck, in case it helps
> anyone else.
> Probably just me being dense.
>
>
> I started down the road of "retrieving an R object is as keywords
> of the r
> object." I figured this was a viable technique to learn first, in
> case "the
> first way of retrieving a R object is as attributes of the r
> object" put up
> a fight. But when I tried:
>
> r['pwr.p.test(h=0.2,power=0.95,sig.level=0.05)']
>
> and similar variations I got something like:
>
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> File "/usr/lib/python2.4/site-packages/rpy.py", line 290, in
> __getitem__
> obj = self.__dict__[name] = self.__dict__.get(name, self.get
> (name))
> rpy.RException: Error in get(x, envir, mode, inherits) : variable
> "pwr.p.test(h=0.2,power=0.95,sig.level=0.05)" was not found
>
> Is there a way to use the "retrieving an R object is as keywords of
> the r
> object" approach, given the example here?
>
> Thanks,
>
> - Michael
>
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