Help on indicator variables
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 at r-project.org [mailto:r-help-bounces at 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 at 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 at 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 at cbs.dk Priv: PDalgd at gmail.com