\Header{make.names}{Make Syntactically Valid Names}
\keyword{character}{make.names}
\begin{Description}\relax
Make syntactically valid names out of character vectors.
\end{Description}
\begin{Usage}
\begin{verbatim}
make.names(names, unique = FALSE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{names}] character vector to be coerced to syntactically valid
names. This is coerced to character if necessary.
\item[\code{unique}] logical; if \code{TRUE}, the resulting elements are
unique.  This may be desired for, e.g., column names.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
A syntactically valid name consists of letters, numbers and the dot or
underline characters and starts with a letter or the dot not followed
by a number.  Names such as \code{".2way"} are not valid, and neither
are the reserved words.

The character \code{"X"} is prepended if necessary.
All invalid characters are translated to \code{"."}.  A missing value
is translated to \code{"NA"}.  Names which match \R{} keywords have a dot
appended to them.  Duplicated values are altered by
\code{\Link{make.unique}}.
\end{Details}
\begin{Value}
A character vector of same length as \code{names} with each changed to
a syntactically valid name.
\end{Value}
\begin{SeeAlso}\relax
\code{\Link{make.unique}},
\code{\Link{names}},
\code{\Link{character}},
\code{\Link{data.frame}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
make.names(c("a and b", "a_and_b"), unique=TRUE)
# "a.and.b"  "a.and.b.1"

data(state)
state.name[make.names(state.name) != state.name] # those 10 with a space
\end{ExampleCode}
\end{Examples}

