Thank you all for your replies. Let me try to explain my point: first of
all, let me clarify that I didn't mean to criticize anyone (or anything).
Secondly, what I meant refers to the fact that I've read on "an R and
S-plus companion to applied regression" about methods to alter the encoding
of factors when using contrasts in regressions. These are options (for
contrasts) that can be easily set as "option('contrasts')". This command
changes the way R creates the dummies out of a factor and various methods
are available.
I was expecting that R might have had something similar that applied to my
case, thus changing the way R attaches numeric values to my dummy variable.
I am just surprised that such option doesn't exist. I was having wrong
expectations.
Thank you all for helping me clarifying this point.
f.
On 23 January 2013 21:55, Rolf Turner <rolf.tur...@xtra.co.nz> wrote:
>
> Given that your labels are "no" and "yes", what do you expect R to
> do? To quote a well-known fortune, "R is lacking a mind_read() function!"
>
> cheers,
>
> Rolf Turner
>
>
> On 01/23/2013 10:58 PM, Francesco Sarracino wrote:
>
>> Thanks,
>> this works! but I am surprised that R has such a strange behavior and that
>> there is no way to control it.
>> BTW, also as.integer(pp)-1 works!
>> Still, it doesn't look to me as a first best.
>> At any rate, thanks a lot for your help.
>> f.
>>
>>
>> On 23 January 2013 10:53, D. Rizopoulos <d.rizopou...@erasmusmc.nl>
>> wrote:
>>
>> check also
>>>
>>> pp <- rep(0:1, 10)
>>> pp <- factor(pp, levels=(0:1), labels=c("no","yes"))
>>>
>>> unclass(pp)
>>> unclass(pp) - 1
>>>
>>>
>>> Best,
>>> Dimitris
>>>
>>>
>>> On 1/23/2013 10:48 AM, Francesco Sarracino wrote:
>>>
>>>> Dear Dimitris,
>>>>
>>>> thanks for your quick reply. I've tried the solutions proposed in 7.10
>>>> How do I convert factors to numeric?
>>>>
>>>> as.numeric(as.character(pp))
>>>> and
>>>> as.numeric(levels(pp))[as.**integer(pp)]
>>>>
>>>> However, whatever I do, I get "Warning message: NAs introduced by
>>>>
>>> coercion"
>>>
>>>> and the output is a vector of NA.
>>>>
>>>> Any ideas?
>>>> f.
>>>>
>>>>
>>>>
>>>> On 23 January 2013 10:39, D. Rizopoulos <d.rizopou...@erasmusmc.nl
>>>> <mailto:d.rizopoulos@**erasmusmc.nl <d.rizopou...@erasmusmc.nl>>>
>>>> wrote:
>>>>
>>>> Check R FAQ 7.10: How do I convert factors to numeric?
>>>>
>>>>
>>>> I hope it helps.
>>>>
>>>> Best,
>>>> Dimitris
>>>>
>>>>
>>>> On 1/23/2013 10:33 AM, Francesco Sarracino wrote:
>>>> > Dear R listers,
>>>> >
>>>> > I am trying to compute the mean of a dummy variable that is
>>>> encoded as a
>>>> > factor. However, even though the levels of my factor are 0 - 1,
>>>> when I
>>>> > compute the mean (after coercing the factor to be
>>>> > numeric), R changes 0 into 1 and 1 into yes, thus altering my
>>>> expected
>>>> > result.
>>>> >
>>>> > Please, consider the following working example:
>>>> > pp <- rep(0:1, 10)
>>>> > pp <- factor(pp, levels=(0:1), labels=c("no","yes"))
>>>> > mean(pp) #this won't work because the argument is not numeric or
>>>> logical
>>>> > mean(as.integer(pp)) # this computes the average, but not on the
>>>> range 0-1,
>>>> > but 1-2. Indeed, the result is 1.5 and not 0.5 as expected.
>>>> >
>>>> > What am I doing wrong?
>>>> > Thanks in advance for your kind support,
>>>> > f.
>>>> >
>>>> >
>>>>
>>>> --
>>>> Dimitris Rizopoulos
>>>> Assistant Professor
>>>> Department of Biostatistics
>>>> Erasmus University Medical Center
>>>>
>>>> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
>>>> Tel: +31/(0)10/7043478 <tel:%2B31%2F%280%2910%**2F7043478>
>>>> Fax: +31/(0)10/7043014 <tel:%2B31%2F%280%2910%**2F7043014>
>>>> Web:
>>>> http://www.erasmusmc.nl/**biostatistiek/<http://www.erasmusmc.nl/biostatistiek/>
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Francesco Sarracino, Ph.D.
>>>> https://sites.google.com/site/**fsarracino/<https://sites.google.com/site/fsarracino/>
>>>>
>>> --
>>> Dimitris Rizopoulos
>>> Assistant Professor
>>> Department of Biostatistics
>>> Erasmus University Medical Center
>>>
>>> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
>>> Tel: +31/(0)10/7043478
>>> Fax: +31/(0)10/7043014
>>> Web:
>>> http://www.erasmusmc.nl/**biostatistiek/<http://www.erasmusmc.nl/biostatistiek/>
>>>
>>>
>>
>>
>
--
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/
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