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  \emph{Group} methods for \code{data.frame}s;
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  \emph{Group} methods for \code{data.frame}s;
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  \code{\link{read.table}},
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  \code{\link{read.table}},
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  \code{\link{make.names}}.
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  \code{\link{make.names}}.
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}
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}
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\examples{
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\examples{
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require(utils)
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L3 <- LETTERS[1:3]
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L3 <- LETTERS[1:3]
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str(d <- data.frame(cbind(x=1, y=1:10), fac=sample(L3, 10, repl=TRUE)))
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(d <- data.frame(cbind(x=1, y=1:10), fac=sample(L3, 10, repl=TRUE)))
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## The same with automatic column names:
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## The same with automatic column names:
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str(     data.frame(cbind(  1,   1:10),     sample(L3, 10, repl=TRUE)))
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data.frame(cbind(  1,   1:10),     sample(L3, 10, repl=TRUE))
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is.data.frame(d)
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is.data.frame(d)
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## do not convert to factor, using I() :
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## do not convert to factor, using I() :
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str(cbind(d, char = I(letters[1:10])), vec.len = 10)
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(dd <- cbind(d, char = I(letters[1:10])))
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rbind(class=sapply(dd, class), mode=sapply(dd, mode))
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stopifnot(1:10 == row.names(d))# {coercion}
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stopifnot(1:10 == row.names(d))# {coercion}
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(d0  <- d[, FALSE]) # NULL data frame with 10 rows
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(d0  <- d[, FALSE]) # NULL data frame with 10 rows
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(d.0 <- d[FALSE, ]) # <0 rows> data frame  (3 cols)
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(d.0 <- d[FALSE, ]) # <0 rows> data frame  (3 cols)