[R] recode: how to avoid nested ifelse

[Neal Fultz]

I would do this to get the highest non-missing level:

x <- pmax(3*cg, 2*hs, es, 0, na.rm=TRUE)

rock chalk...

-nfultz

On Fri, Jun 07, 2013 at 06:24:50PM -0700, Joshua Wiley wrote:
> Hi Paul,
> 
> Unless you have truly offended the data generating oracle*, the
> pattern: NA, 1, NA, should be a data entry error --- graduating HS
> implies graduating ES, no?  I would argue fringe cases like that
> should be corrected in the data, not through coding work arounds.
> Then you can just do:
> 
> x <- do.call(paste0, list(es, hs, cg))
> 
> > table(factor(x, levels = c("000", "100", "110", "111"), labels = c("none", "es","hs", "cg")))
> none   es   hs   cg
>    4    1    1    2
> 
> Cheers,
> 
> Josh
> 
> *Drawn from comments by Judea Pearl one lively session.
> 
> 
> On Fri, Jun 7, 2013 at 6:13 PM, Paul Johnson <pauljohn32 at gmail.com> wrote:
> > In our Summer Stats Institute, I was asked a question that amounts to
> > reversing the effect of the contrasts function (reconstruct an ordinal
> > predictor from a set of binary columns). The best I could think of was to
> > link together several ifelse functions, and I don't think I want to do this
> > if the example became any more complicated.
> >
> > I'm unable to remember a less error prone method :). But I expect you might.
> >
> > Here's my working example code
> >
> > ## Paul Johnson <pauljohn at ku.edu>
> > ## 2013-06-07
> >
> > ## We need to create an ordinal factor from these indicators
> > ## completed elementary school
> > es <- c(0, 0, 1, 0, 1, 0, 1, 1)
> > ## completed high school
> > hs <- c(0, 0, 1, 0, 1, 0, 1, 0)
> > ## completed college graduate
> > cg <- c(0, 0, 0, 0, 1, 0, 1, 0)
> >
> > ed <- ifelse(cg == 1, 3,
> >              ifelse(hs == 1, 2,
> >                     ifelse(es == 1, 1, 0)))
> >
> > edf <- factor(ed, levels = 0:3,  labels = c("none", "es", "hs", "cg"))
> > data.frame(es, hs, cg, ed, edf)
> >
> > ## Looks OK, but what if there are missings?
> > es <- c(0, 0, 1, 0, 1, 0, 1, 1, NA, NA)
> > hs <- c(0, 0, 1, 0, 1, 0, 1, 0, 1, NA)
> > cg <- c(0, 0, 0, 0, 1, 0, 1, 0, NA, NA)
> > ed <- ifelse(cg == 1, 3,
> >              ifelse(hs == 1, 2,
> >                     ifelse(es == 1, 1, 0)))
> > cbind(es, hs, cg, ed)
> >
> > ## That's bad, ifelse returns NA too frequently.
> > ## Revise (becoming tedious!)
> >
> > ed <- ifelse(!is.na(cg) & cg == 1, 3,
> >              ifelse(!is.na(hs) & hs == 1, 2,
> >                     ifelse(!is.na(es) & es == 1, 1,
> >                            ifelse(is.na(es), NA, 0))))
> > cbind(es, hs, cg, ed)
> >
> >
> > ## Does the project director want us to worry about
> > ## logical inconsistencies, such as es = 0 but cg = 1?
> > ## I hope not.
> >
> > Thanks in advance, I hope you are having a nice summer.
> >
> > pj
> >
> > --
> > Paul E. Johnson
> > Professor, Political Science      Assoc. Director
> > 1541 Lilac Lane, Room 504      Center for Research Methods
> > University of Kansas                 University of Kansas
> > http://pj.freefaculty.org               http://quant.ku.edu
> >
> >         [[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.
> 
> 
> 
> -- 
> Joshua Wiley
> Ph.D. Student, Health Psychology
> University of California, Los Angeles
> http://joshuawiley.com/
> Senior Analyst - Elkhart Group Ltd.
> http://elkhartgroup.com
> 
> ______________________________________________
> 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.