Thank you Peter.
nls() & predict() seems to do the job.
dror

-------------------------

On Wed, Dec 30, 2009 at 8:10 PM, Peter Ehlers <ehlers@ucalgary.ca> wrote:

> Sounds like you might want to use nls() to fit the data
> and then use either curve() or predict() to do the
> plotting.
>
>  -Peter Ehlers
>
> Dror D Lev wrote:
>
>> Hi,
>>
>> I tried to be comprehensive but Jim's comment is indeed in place.
>>
>> I have data of a practice experiment where people practice a certain motor
>> task and time-to-completion was recorded.
>> Appropriately, the time measure declines as practice goes on. And, again
>> appropriately, the relation seems to be non-linear. It looks like y=1/x
>> but
>> much less steep.
>> I understand that the general case of such functions is called
>> power-function.
>>
>> So what I'm looking for is something like abline() with a power-function
>> fit
>> (rather then a linear one).
>>
>> Jim is also correct writing that I would like to have separate fits for
>> 'c'
>> and 'nc'.
>> Of course this can be achieved using subset() but, as Dennis wrote, some
>> graphic functions include an option to graph the data by groups.
>>
>> Thanks again for any tip or reference.
>>
>> dror
>>
>> -------------
>>
>> On Tue, Dec 29, 2009 at 10:56 PM, jim holtman <jholtman@gmail.com> wrote:
>>
>>  It would help if you were more explicit on what you were trying to look
>>> at.  I assume that you want two curves ('c' and'nc') on one graphs and
>>> you
>>> can do that with the basic plot routines, or you can use the 'lattice'
>>> package, but without knowing what you are looking for, it is hard to
>>> tell.
>>>
>>> On Tue, Dec 29, 2009 at 3:33 PM, Dror D Lev <dror.teach@gmail.com>
>>> wrote:
>>>
>>>  Hello,
>>>>
>>>> I have practice data of motor action in the format:
>>>>
>>>> S  | Cond. | Time
>>>> ----+---------+--------
>>>> 01 |  c      |  1.23
>>>> 01 |  nc    |  0.89
>>>> 02 |  c      |  2.15
>>>> 02 |  nc    |  1.80
>>>> .....
>>>>
>>>> I want to look at the learning curves graphically.
>>>>
>>>> I will appreciate pointers to relevant functions / packages.
>>>>
>>>> Thanks in advance,
>>>> dror
>>>>
>>>>       [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
>>>> R-help@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<
>>>> http://www.r-project.org/posting-guide.html>
>>>>
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>>
>>>
>>> --
>>> Jim Holtman
>>> Cincinnati, OH
>>> +1 513 646 9390
>>>
>>> What is the problem that you are trying to solve?
>>>
>>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@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.
>>
>>
>>
> --
> Peter Ehlers
> University of Calgary
> 403.202.3921
>

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