Re: [R] problems with coercing a factor to be numeric
Dear Ellison,
thanks a lot for your reply. Your explanation makes things much clearer.
Sincerely,
f.
On 24 January 2013 05:58, S Ellison wrote:
>
>
> On 23 Jan 2013, at 21:36, "Francesco Sarracino"
> wrote:
>
> > 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.
>
> Such options do exist, but at modelling time, not factor
> creation/conversion time.
>
> When created, by calls to 'factor' or in functions like 'read.table',
> factors are stored internally as integers with a list of labels (what you
> see as factor levels) that go with each integer. Those internal integers
> start at 1 and go up. You can set the ordering of those labels (by
> specifying the "levels" argument in factor()) so that, for example, yes and
> no can be associated with (numeric) factor levels 1 and 2 respectively
> instead of the default ordering which would put 'no' alphabetically before
> 'yes'. (I find this choice particularly useful for orderings like "high",
> "medium", "low" for which the alphabetic ordering is not exactly intuitive;
> similarly alphabetic ordering puts '1', '2', '10' in the order '1', '10',
> '2' and so on, so that often needs specifying manually. It's also useful to
> specify levels if you want things like boxplots to come out in a particular
> order, as boxplots by default use the order of the factor levels).
> The internal integer values are returned by 'as numeric'. If your factor
> level labels - which are always character - are also interpretable as
> numbers, you need 'as.character' to return the character strings and then
> 'as.numeric' to convert those.
>
> Now, up to this point you just have more or less arbitrary integers
> asociated with the original factor levels (the degree of arbitrariness
> depends on whether you specified the level order or let R use its default).
> These integers are not the contrasts used in model fitting. Contrasts are
> set at model matrix building time; they are not a fixed attribute of the
> factor. The internal numbering of levels affects contrasts only to the
> extent that the numerical values used in setting contrasts are usually in
> the same order as the factor levels. You can inspect the functions used to
> associate contrasts with factor levels by using options("contrasts"). You
> can inspect the numerical values that would currently be used for a given
> factor with a call to contrasts(). You can change the contrast asignments
> globally using options() or explicitly in some model calls (lm, for
> example, has a contrasts argument) and if you like you can write your own
> contrast functions to set any values you like. The most common are
> probably treatment contrasts, which set the first factor level as intercept
> and the rest as (unit) differences from that, and sum to zero contrasts
> which do what they say, setting contrasts that sum to zero by choosing a
> set like (-1, 0, 1).
>
> So you actually have a great deal of control over both the order in which
> labels are associated with factor levels and the (separate) values of
> contrasts associated with those factor levels at modelling time.
>
> The cost of that control is some complexity, and the time needed to learn
> what's going on to use it all properly.
>
> Hope that helps ...
>
>
> S Ellison
>
> ***
> This email and any attachments are confidential. Any u...{{dropped:18}}
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Re: [R] problems with coercing a factor to be numeric
On 23 Jan 2013, at 21:36, "Francesco Sarracino" wrote:
> 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.
Such options do exist, but at modelling time, not factor creation/conversion
time.
When created, by calls to 'factor' or in functions like 'read.table', factors
are stored internally as integers with a list of labels (what you see as factor
levels) that go with each integer. Those internal integers start at 1 and go
up. You can set the ordering of those labels (by specifying the "levels"
argument in factor()) so that, for example, yes and no can be associated with
(numeric) factor levels 1 and 2 respectively instead of the default ordering
which would put 'no' alphabetically before 'yes'. (I find this choice
particularly useful for orderings like "high", "medium", "low" for which the
alphabetic ordering is not exactly intuitive; similarly alphabetic ordering
puts '1', '2', '10' in the order '1', '10', '2' and so on, so that often needs
specifying manually. It's also useful to specify levels if you want things like
boxplots to come out in a particular order, as boxplots by default use the
order of the factor levels).
The internal integer values are returned by 'as numeric'. If your factor level
labels - which are always character - are also interpretable as numbers, you
need 'as.character' to return the character strings and then 'as.numeric' to
convert those.
Now, up to this point you just have more or less arbitrary integers asociated
with the original factor levels (the degree of arbitrariness depends on whether
you specified the level order or let R use its default). These integers are not
the contrasts used in model fitting. Contrasts are set at model matrix building
time; they are not a fixed attribute of the factor. The internal numbering of
levels affects contrasts only to the extent that the numerical values used in
setting contrasts are usually in the same order as the factor levels. You can
inspect the functions used to associate contrasts with factor levels by using
options("contrasts"). You can inspect the numerical values that would currently
be used for a given factor with a call to contrasts(). You can change the
contrast asignments globally using options() or explicitly in some model calls
(lm, for example, has a contrasts argument) and if you like you can write your
own contrast functions to set any values you!
like. The most common are probably treatment contrasts, which set the first
factor level as intercept and the rest as (unit) differences from that, and sum
to zero contrasts which do what they say, setting contrasts that sum to zero by
choosing a set like (-1, 0, 1).
So you actually have a great deal of control over both the order in which
labels are associated with factor levels and the (separate) values of contrasts
associated with those factor levels at modelling time.
The cost of that control is some complexity, and the time needed to learn
what's going on to use it all properly.
Hope that helps ...
S Ellison
***
This email and any attachments are confidential. Any use...{{dropped:8}}
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and provide commented, minimal, self-contained, reproducible code.
Re: [R] problems with coercing a factor to be numeric
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 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
>> 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 >>> >
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
Fax: +31/(0)10/7043014
Web:
http://www.erasmusmc.nl/**biostatistiek/
Re: [R] problems with coercing a factor to be numeric
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 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 mailto: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
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/
--
Francesco Sarracino, Ph.D.
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/
__
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.
Re: [R] problems with coercing a factor to be numeric
To find the proportion of "yes"s in pp you can use
mean(pp == "yes")
and avoid the conversion of a factor to integer (and
subtracting 1). The above works for character and factor
pp.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -Original Message-
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of Francesco Sarracino
> Sent: Wednesday, January 23, 2013 1:59 AM
> To: D. Rizopoulos
> Cc: R help
> Subject: Re: [R] problems with coercing a factor to be numeric
>
> 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 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 > > <mailto: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
> > > Fax: +31/(0)10/7043014
> > > Web: http://www.erasmusmc.nl/biostatistiek/
> > >
> > >
> > >
> > >
> > > --
> > > Francesco Sarracino, Ph.D.
> > > 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/
> >
>
>
>
> --
> Francesco Sarracino, Ph.D.
> https://sites.google.com/site/fsarracino/
>
> [[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.
__
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] problems with coercing a factor to be numeric
On Jan 23, 2013, at 1:58 AM, 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.
I think it is rather strange that you are criticising R because the
mean or sum functions won't coerce factors to numeric class. R is
already very loosely typed. It has a fairly limited number of object
classes and there is widespread class coercion when it is appropriate.
Can you explain why you believed factors or by logical extension
character classed variables should get implicitly coerced by all
mathematical functions?
--
David.
f.
On 23 January 2013 10:53, D. Rizopoulos
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 mailto: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
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/
--
Francesco Sarracino, Ph.D.
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/
--
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/
[[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.
David Winsemius, MD
Alameda, CA, USA
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] problems with coercing a factor to be numeric
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 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 > > 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
> > Fax: +31/(0)10/7043014
> > Web: http://www.erasmusmc.nl/biostatistiek/
> >
> >
> >
> >
> > --
> > Francesco Sarracino, Ph.D.
> > 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/
>
--
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/
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Re: [R] problems with coercing a factor to be numeric
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 > 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
> Fax: +31/(0)10/7043014
> Web: http://www.erasmusmc.nl/biostatistiek/
>
>
>
>
> --
> Francesco Sarracino, Ph.D.
> 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/
__
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.
Re: [R] problems with coercing a factor to be numeric
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 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
> Fax: +31/(0)10/7043014
> Web: http://www.erasmusmc.nl/biostatistiek/
--
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/
[[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.
Re: [R] problems with coercing a factor to be numeric
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
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/
__
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.
[R] problems with coercing a factor to be numeric
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.
--
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/
[[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.
