What Bill says, plus the fact that the default handling of logicals in
modelling is to convert them to factors and then use treatment contrasts, which
will effectively give you the right indicator variables automagically (This in
contrast to SAS where you can confuse yourself by declaring a 0/1 variable as a
CLASS variable):
> cond <- rep(c(TRUE, FALSE),4)
> y <- rnorm(8)
> lm(y~cond)
Call:
lm(formula = y ~ cond)
Coefficients:
(Intercept) condTRUE
-0.5741 1.1845
> lm(y~as.numeric(cond))
Call:
lm(formula = y ~ as.numeric(cond))
Coefficients:
(Intercept) as.numeric(cond)
-0.5741 1.1845
On Mar 21, 2013, at 15:49 , William Dunlap wrote:
> I would use a logical variable, with values TRUE and FALSE, instead
> of a numeric indicator. E.g., I find the following easier to follow
> bL <- ABS==1 | DEFF==1
> if (any(bL)) { do.this() }
> than
> bN <- ifelse(ABS == 1 | DEFF == 1, 1, 0)
> if (any(bN == 1)) { do.this() }
> The latter leaves me wondering what other values bN might have;
> the former makes it clear this is a TRUE/FALSE dichotomy.
>
> Logicals get converted to numbers (FALSE->0, TRUE->1) when used in
> arithmetic so you can do, e.g., mean(bL) to see what proportion of
> your cases satisfy the condition.
>
> 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 Tasnuva Tabassum
>> Sent: Thursday, March 21, 2013 6:03 AM
>> To: R help
>> Subject: [R] Help on indicator variables
>>
>> I have two indicator variables ABS and DEFF. I want to create another
>> indicator variable which will take value 1 if either ABS=1 or DEFF=1.
>> Otherwise, it will take value 0. How can I make that?
>>
>> [[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
> 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 Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
______________________________________________
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.
