\HeaderA{matchprobes}{A function to match a query sequence to the sequences of a set of
probes.}{matchprobes}
\keyword{manip}{matchprobes}
\begin{Description}\relax
The \code{query} sequence, a character string (probably representing
a transcript of interest), is scanned for the presence of exact
matches to the sequences in the character vector \code{records}.
The indices of the set of matches are returned.
\end{Description}
\begin{Usage}
\begin{verbatim}
matchprobes(query, records, probepos=FALSE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{query}] A character vector. For example, each element may represent
a gene (transcript) of interest. See Details.
\item[\code{records}] A character vector. For example, each element may represent
the probes on a DNA array.
\item[\code{probepos}] A logical value. If TRUE, return also the start
positions of the matches in the query sequence.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
\code{\LinkA{toupper}{toupper}} is applied to the arguments \code{query} and
\code{records} before matching. The intention of this is to make
the matching case-insensitive.
The matching is done using the C library function \code{strstr}. It
might be nice to explore other possibilities.
\end{Details}
\begin{Value}
A list.
Its first element is a list of the same length as the input vector.
Each element of the list is a numeric vector containing the indices of
the probes that have a perfect match in the query
sequence.

If \code{probepos} is TRUE,
the returned list has a second element: it is of the same shape
as described above, and gives the respective positions of the
matches.
\end{Value}
\begin{Author}\relax
R. Gentleman, Laurent Gautier, Wolfgang Huber
\end{Author}
\begin{Examples}
\begin{ExampleCode}
  ## The main intention for this function is together with the probe
  ## tables from the "probe" data packages, e.g.:
  ## > library(hgu95av2probe)
  ## > data(probe)
  ## > seq <- probe$sequence
  ##
  ## Since we do not want to be dependent on the presence of this 
  ## data package, for the sake of example we simply simulate some
  ## probe sequences:

  bases <- c("A", "C", "G", "T")
  seq   <- sapply(1:1000, function(x) paste(bases[ceiling(4*runif(256))], collapse=""))

  w1 <- seq[20:22]
  w2 <- complementSeq(w1, start=13, stop=13)
  w  <- c(w1, w2)

  matchprobes(w, seq)
  matchprobes(w, seq, probepos=TRUE)
\end{ExampleCode}
\end{Examples}