rampOgive warning

[Maschette]

When running rampOgive it may be worth putting a warning in place if there is a difference in size between the xrange and the length steps in the vector.

for example:

x <- seq(150,450,50)
p <- rampOgive(x,300,80)
p 
[1] 0.0 0.0 0.0 0.5 1.0 1.0 1.0

in this situation the xrange would actually be 100 mm as the length steps are 50mm each