From: Charilaos Skiadas <cskiadas_at_gmail.com>

Date: Tue, 06 May 2008 15:25:40 -0400

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. Received on Tue 06 May 2008 - 19:29:16 GMT

Date: Tue, 06 May 2008 15:25:40 -0400

I would actually go with this:

bits=c(1, 0, 1, 1, 0)

paste("X", which(bits==1), sep=".",collapse="+")

No need for the vars variable. Though admittedly it breaks down if bits is identically 0.

Haris Skiadas

Department of Mathematics and Computer Science
Hanover College

On May 6, 2008, at 3:11 PM, Jorge Ivan Velez wrote:

> Hi Esmail,

*>
**> Try this:
**>
**> vars=c('X.1', 'X.2', 'X.3', 'X.4', 'X.5')
**> bits=c(1, 0, 1, 1, 0)
**> paste(vars[which(bits==1)],collapse="+")
**>
**> HTH,
**>
**> Jorge
**>
**>
**>
**> On Tue, May 6, 2008 at 3:06 PM, Esmail Bonakdarian
**> <esmail.js_at_gmail.com>
**> wrote:
**>
**>> Hello,
**>>
**>> Still a newbie with R, though I have learned a lot from reading
**>> this list. I'm hoping someone can help with this question:
**>>
**>> I have two vectors, one for variables, and one for bits.
**>>
**>> I want to build a string (really a formula) based on the values in my
**>> vector of 1s and 0s in bits. If I have a one, I want to include the
**>> corresponding entry in the vars vector, otherwise ignore it. Of
**>> course
**>> the "bits" vector will not stay the same.
**>>
**>> So for example:
**>>
**>> vars=c('X.1', 'X.2', 'X.3', 'X.4', 'X.5')
**>>
**>> bits=c(1, 0, 1, 1, 0)
**>> ones=which(bits==1)
**>>
**>> should yield:
**>>
**>> "X.1 + X.3 + X.4"
**>>
**>> where as
**>>
**>> bits=c(1, 1, 0, 0, 0)
**>>
**>> would yield
**>>
**>> "X.1 + X.2"
**>>
**>> the "which" operator gives me the index values, is there an easy and
**>> *efficient* way to build this string so that I can pass it on to glm?
**>> I can probably hack some ugly code together to do this, but it won't
**>> be efficient, and it won't be elegant :-)
**>>
**>> Can anyone help?
**>>
**>> Thanks!
*

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