[R] Problem with lm

[Greg Snow]

This error can still occur even if something is passed as the y
parameter to the function.  There are several things that can
complicate the process (and I don't remember exactly which one causes
the problem in this case).  Here are a couple:

In the original function, y is a parameter, but it is never actually
used before the call to lm, which means that y is really a promise to
evaluate whatever was passed to the function, but does not yet contain
the actual y values.

The lm function calls the model.frame function which calls the
model.frame.default function, which may call another function, which
of all those function environments should it look for the variable y
in?  (it seems obvious to us, but the computer is not as smart), there
is also the environment that the formula was defined in that is used
for some things.

Possibly others as well.

In either case if an explicit data frame is created (which will force
the evaluation of the promise for y) and passed to the data argument
of lm, then all these functions know exactly where to look to find the
variables in the formula and don't need to worry about parent frames
and parent environments.

This document: http://developer.r-project.org/nonstandard-eval.pdf
gives more detail.

On Thu, Nov 1, 2012 at 10:23 AM, Mick Cooney <mickcooney at gmail.com> wrote:
> But the 'y' is a parameter to the function, so does this mean that the
> error is occurring when the function is invoked without that
> parameter?
>
> On 1 November 2012 16:02, Greg Snow <538280 at gmail.com> wrote:
>> Yes, it is most likely due to scoping.  It is safest to create a data
>> frame with all the data in it, then pass that to the data argument of
>> lm.
>>
>> On Thu, Nov 1, 2012 at 2:25 AM, Eva Prieto Castro <evapcastro at yahoo.es> wrote:
>>> Hi,
>>>
>>> I have a problem in relation with a packahe I made. It runs on my machine (Windows, where I made the package), and it runs in a Mac machine, but it does not run in another Mac machine with the same R version.
>>>
>>> The part of the code is giving problems:
>>>
>>> singleCosinor <- function(t, y, period=24) {
>>>   x1 <- cos(2 * pi * t / period)
>>>   x2 <- sin(2 * pi * t / period)
>>>   single <- lm (y ~ x1 + x2)
>>>   return(single)
>>> }
>>>
>>> The error:
>>>
>>> Error en eval(expr, envir, enclos) : objeto 'y' no encontrado
>>>
>>> Can it be in relation with scoping?.
>>>
>>> Thanks in advance.
>>>
>>> Eva
>>>
>>>         [[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.
>>>
>>
>>
>>
>> --
>> Gregory (Greg) L. Snow Ph.D.
>> 538280 at gmail.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.
>
>
>
> --
> Mick Cooney
> mickcooney at gmail.com



-- 
Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com