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% File src/library/base/man/switch.Rd
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% File src/library/base/man/switch.Rd
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% Part of the R package, http://www.R-project.org
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% Part of the R package, http://www.R-project.org
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% Copyright 1995-2010 R Core Team
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% Copyright 1995-2013 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{switch}
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\name{switch}
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\alias{switch}
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\alias{switch}
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\title{Select One of a List of Alternatives}
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\title{Select One of a List of Alternatives}
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\details{
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\details{
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  \code{switch} works in two distinct ways depending whether the first
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  \code{switch} works in two distinct ways depending whether the first
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  argument evaluates to a character string or a number.
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  argument evaluates to a character string or a number.
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  If the value of \code{EXPR} is not a character string it is coerced to
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  If the value of \code{EXPR} is not a character string it is coerced to
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  integer.  If this is between 1 and \code{nargs()-1} then the
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  integer.  Note that this also happens for \code{\link{factor}}s, with
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  corresponding element of \code{\dots} is evaluated and the result
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  a warning, as typically the character level is meant.  If the integer
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  is between 1 and \code{nargs()-1} then the corresponding element of
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  returned: thus if the first argument is \code{3} then the fourth
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  \code{\dots} is evaluated and the result returned: thus if the first
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  argument is evaluated and returned.
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  argument is \code{3} then the fourth argument is evaluated and
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  returned.
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  If \code{EXPR} evaluates to a character string then that string is
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  If \code{EXPR} evaluates to a character string then that string is
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  matched (exactly)to the names of the elements in \code{\dots}.  If
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  matched (exactly) to the names of the elements in \code{\dots}.  If
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  there is a match then that element is evaluated unless it is missing,
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  there is a match then that element is evaluated unless it is missing,
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  in which case the next non-missing element is evaluated, so for
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  in which case the next non-missing element is evaluated, so for
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  example \code{switch("cc", a = 1, cc =, cd =, d = 2)} evaluates to
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  example \code{switch("cc", a = 1, cc =, cd =, d = 2)} evaluates to
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  \code{2}.  If there is more than one match, the first matching element
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  \code{2}.  If there is more than one match, the first matching element
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  is used.  In the case of no match, if there is a unnamed element of
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  is used.  In the case of no match, if there is a unnamed element of
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for(ch in ccc)
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for(ch in ccc)
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    cat(ch,":", switch(EXPR = ch, a = 1, b = 2:3), "\n")
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    cat(ch,":", switch(EXPR = ch, a = 1, b = 2:3), "\n")
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for(ch in ccc)
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for(ch in ccc)
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    cat(ch,":", switch(EXPR = ch, a =, A = 1, b = 2:3, "Otherwise: last"),"\n")
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    cat(ch,":", switch(EXPR = ch, a =, A = 1, b = 2:3, "Otherwise: last"),"\n")
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## switch(f, *) with a factor f
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ff <- gl(3,1, labels=LETTERS[3:1])
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ff[1] # C
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## so one might expect " is C" here, but
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switch(ff[1], A = "I am A", B="Bb..", C=" is C")# -> "A"
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## so we give a warning
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## Numeric EXPR does not allow a default value to be specified
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## Numeric EXPR does not allow a default value to be specified
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## -- it is always NULL
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## -- it is always NULL
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for(i in c(-1:3, 9))  print(switch(i, 1, 2 , 3, 4))
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for(i in c(-1:3, 9))  print(switch(i, 1, 2 , 3, 4))
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## visibility
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## visibility