#' gsplot curve

#'

#' Plot a mathematical function of x on a new or existing plotting region.

#'

#' @param object gsplot object

#' @param \dots Further graphical parameters may also be supplied as arguments. See 'Details'.

#'

#' @details Additional graphical parameter inputs:

#' \itemize{

#' \item{\code{expr}} {mathematic function in terms of x}

#' \item{\code{from}} {x value indicating the beginning of the plotted function}

#' \item{\code{to}} {x value indicating the end of the plotted function}

#' \item{\code{n}} {integer, number of x values at which to evaluate {\code{expr}}}

#' \item{\code{add}} {logical, TRUE=add to existing plot, FALSE=create new plot (default)}

#' \item{\code{xlim}} {vector indicating the lower and upper x values of the plotting window}

#' \item{\code{ylim}} {vector indicating the lower and upper y values of the plotting window}

#' \item{\code{type}} {plot type, where 'l'=line, 'p'=point, etc}

#' \item{\code{log}} {string indicating axes to have a log scale, where ""=none, "x"=x-axis, "y"=y-axis, and "xy"=both axes}

#' \item{\code{col}} {line color}

#' \item{\code{lty}} {line type}

#' \item{\code{lwd}} {line width}

#' }

#'

#' @rdname curve

#' @export

#' @importFrom lazyeval lazy lazy_eval

#' @examples

#' gs <- gsplot() %>%

#' points(x=c(1:5, 3.5), y=c(1:5, 6), legend.name="Stuff") %>%

#' lines(x=2:6, y=2:6, ylim=c(0,10)) %>%

#' axis(side=c(1,2),labels=TRUE) %>%

#' curve(x^3, from=0, to=10, col="blue", legend.name="x^3") %>%

#' legend("topright")

#' gs

#'

#' gs <- gsplot() %>%

#' curve(sin(x), from=-2*pi, to=2*pi, legend.name="sin(x)") %>%

#' legend()

#' gs

curve <- function(object, ...) {

override("graphics", "curve", object, ...)

}

curve.gsplot <- function(object, expr, ..., legend.name=NULL, side=c(1,2)){

expr <- lazy(expr)

arguments = set_args('curve',...)

dots = lazy_dots(...)

increment <- (arguments$to-arguments$from)/10000

x <- seq(arguments$from, arguments$to, by=increment)

y <- lazy_eval(expr, data.frame(x=x))

arguments = set_args(fun.name = 'lines', x=x, y=y, lazy_eval(dots[!names(dots) %in% c('from','to')]))

to.gsplot <- list(list(arguments = arguments, gs.config=list(legend.name = legend.name, side = side))) %>%

setNames('lines')

object <- gsplot(append(object, to.gsplot))

return(object)

}