Thanks all. you guys are really helpful.


On Fri, Mar 22, 2013 at 2:48 PM, peter dalgaard <pdalgd@gmail.com> wrote:

> 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-bounces@r-project.org [mailto:r-help-bounces@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.mes@cbs.dk  Priv: PDalgd@gmail.com
>
>

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