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% File src/library/grDevices/man/n2mfrow.Rd
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% File src/library/grDevices/man/n2mfrow.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2007 R Core Team
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% Copyright 1995-2019 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{n2mfrow}
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\name{n2mfrow}
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\alias{n2mfrow}
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\alias{n2mfrow}
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\title{Compute Default mfrow From Number of Plots}
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\title{Compute Default 'mfrow' From Number of Plots}
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\description{
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\description{
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  Easy setup for plotting multiple figures (in a rectangular layout) on
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  Easy setup for plotting multiple figures (in a rectangular layout) on
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  one page.  This computes a sensible default for
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  one page.  This computes a sensible default for
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  \code{\link{par}(mfrow)}.
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  \code{\link{par}(mfrow)}.
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}
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}
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\usage{
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\usage{
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n2mfrow(nr.plots)
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n2mfrow(nr.plots, asp = 1)
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}
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}
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\arguments{
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\arguments{
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  \item{nr.plots}{integer; the number of plot figures you'll want to draw.}
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  \item{nr.plots}{integer; the number of plot figures you'll want to draw.}
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  \item{asp}{positive number; the target aspect ratio (columns / rows) in
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    the output.  Was implicitly hardwired to \code{1}; because of that and
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    back compatibility, there is a somewhat discontinuous behavior when
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    varying \code{asp} around 1, for \code{nr.plots <= 12}.}
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}
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}
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\value{
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\value{
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  A length two integer vector \code{nr, nc} giving the number of rows
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  A length-two integer vector \code{(nr, nc)} giving the positive number of rows
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  and columns, fulfilling \code{nr >= nc >= 1} and \code{nr * nc >= nr.plots}.
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  and columns, fulfilling \code{nr * nc >= nr.plots}, and currently, for
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  \code{asp = 1}, \code{nr >= nc >= 1}.
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}
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}
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\note{
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  Conceptually, this is a quadratic integer optimization problem, with
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  inequality constraints \eqn{nr >= 1}, \eqn{nc >= 1}, and
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  \eqn{nr.plots >= nr*nc} (and possibly \code{nr >= asp*nc}),
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  and \emph{two} objective functions which would have to be combined via a
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  tuning weight, say \eqn{w}, to, e.g.,
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  \eqn{(nr.plots - nr*nc)  + w |nr/nc - asp|}.
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  The current algorithm is simple and not trying to solve one of these
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\author{Martin Maechler}
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  optimization problems.
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}
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\author{Martin Maechler; suggestion of \code{asp} by Michael Chirico.}
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\seealso{\code{\link{par}}, \code{\link{layout}}.}
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\seealso{\code{\link{par}}, \code{\link{layout}}.}
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\examples{
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\examples{
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require(graphics)
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require(graphics)
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n2mfrow(8) # 3 x 3
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n2mfrow(8) # 3 x 3
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op <- par(mfrow = n2mfrow(n))
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op <- par(mfrow = n2mfrow(n))
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for (j in 1:n)
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for (j in 1:n)
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   plot(x, x^j, main = substitute(x^ exp, list(exp = j)), type = "l",
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   plot(x, x^j, main = substitute(x^ exp, list(exp = j)), type = "l",
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   col = "blue")
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   col = "blue")
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sapply(1:10, n2mfrow)
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sapply(1:14, n2mfrow)
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sapply(1:14, n2mfrow, asp=16/9)
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}
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}
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\keyword{dplot}
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\keyword{dplot}
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\keyword{utilities}
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\keyword{utilities}