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!
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@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!
>
> ______________________________________________
> 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.
[[alternative HTML version deleted]]
Esmail Bonakdarian 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!Depending upon other factors, there may be a better and more general approach to what you are trying to do relative to selecting subsets of IV's. However, given the information you have provided: vars <- c('X.1', 'X.2', 'X.3', 'X.4', 'X.5') bits <- c(1, 0, 1, 1, 0) > paste(vars[bits == 1], collapse = " + ") [1] "X.1 + X.3 + X.4" bits <- c(1, 1, 0, 0, 0) > paste(vars[bits == 1], collapse = " + ") [1] "X.1 + X.2" You will then need to use as.formula() to coerce the resultant vectors before passing them to the model function. HTH, Marc Schwartz