[R] gsub() on Matrix

[Peter Dalgaard]

Tony Plate <tplate at acm.org> writes:

> Many more recent regular expression implementations have ways of
> indicating a match on a word boundary.  It's usually "\b".
....

Another idea is that if what you need is something that is parseable
as a model formula RHS, then you might want to parse first and
substitute later. Something along these lines:

> e <- parse(text="x1 + x3 + x4 + x5 + x1:x3 + x1:x4")[[1]]
> repl = lapply(c("i7", "i14", "i13", "d2", "i8", "i5"),as.name)
> names(repl)<-paste("x",1:6,sep="")
> eval(substitute(substitute(e,repl),list(e=e)))
i7 + i13 + d2 + i8 + i7:i13 + i7:d2


> At Wednesday 09:07 PM 10/27/2004, Kevin Wang wrote:
> >Suppose I've got a matrix, and the first few elements look like
> >   "x1 + x3 + x4 + x5 + x1:x3 + x1:x4"
> >   "x1 + x2 + x3 + x5 + x1:x2 + x1:x5"
> >   "x1 + x3 + x4 + x5 + x1:x3 + x1:x5"
> >and so on (have got terms from x1 ~ x14).
> >
> >If I want to replace all the x1 with i7, all x2 with i14, all x3 with i13,
> >for example.  Is there an easy way?
> >
> >I tried to put what I want to replace in a vector, like:
> >  repl = c("i7", "i14", "i13", "d2", "i8", "i5",
> >           "i6", "i3", "A", "i9", "i2",
> >           "i4", "i15", "i21")
> >and have another vector, say:
> >   > orig
> >  [1] "x1"  "x2"  "x3"  "x4"  "x5"  "x6"  "x7"  "x8"  "x9"  "x10"
> >[11] "x11" "x12" "x13" "x14"
> >
> >Then I tried something like
> >   gsub(orig, repl, mat)
> >## mat is the name of my matrix
> >
> >but it didn't work *_*.....it would replace terms like x10 with i70.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907