Compute the coordinates of an envelop

envelop eases the computation of the polygons described by to set of y coordinates along the x-axis. Optionally, the polygons could be added on the current plot.

envelop(x, upper, lower = rep(0, length(upper)), add = TRUE, ...)

Arguments

x	vectors containing the x coordinates.
upper	the y coordinates of the upper values.
lower	the y coordinates of the lower values.
add	a logical. If TRUE the envelop is drawn as a polygon (default behavior).
...	additional arguments to be passed to graphics::polygon() function.

Value

The coordinates of the envelop are returned if assigned.

Examples

plot0(c(0, 10), c(0, 10))
sz <- 100
seqx <- seq(0, 10, length.out = sz)
seqy1 <- 0.2 * seqx * runif(sz, 0, 1)
seqy2 <- 4 + 0.25 * seqx * runif(sz, 0, 1)
seqy3 <- 8 + 0.25 * seqx * runif(sz, 0, 1)
envelop(seqx, seqy1, seqy2, col = 'grey85', border = NA)
envelop(seqx, seqy2, seqy3, col = 'grey25', border = NA)