expand {intervals} | R Documentation |
It is often useful to shrink or grow each interval in a set of
intervals: to smooth over small, uninteresting gaps, or to address
possible imprecision resulting from floating point arithmetic. The
expand
and contract
methods implement this, using either
absolute or relative difference.
## S4 method for signature 'Intervals_virtual' expand(x, delta = 0, type = c("absolute", "relative")) ## S4 method for signature 'Intervals_virtual' contract(x, delta = 0, type = c("absolute", "relative"))
x |
An |
delta |
A non-negative adjustement value. A vector is permitted, and its entries will be recycled if necessary. |
type |
Should adjustment be based on relative or absolute difference. When
|
A single object of appropriate class, with endpoint positions adjusted
as requested. Expansion returns an object with the same dimension as
x
; contraction may lead to the elimination of now-empty rows.
Here, the relative difference between x and y is |x - y|/max(|x|, |y|).
# Using adjustment to remove small gaps x <- Intervals( c(1,10,100,8,50,200), type = "Z" ) close_intervals( contract( reduce( expand(x, 1) ), 1 ) ) # Finding points for which, as a result of possible floating point # error, intersection may be ambiguous. Whether y1 intersects y2[2,] # depends on precision. delta <- .Machine$double.eps^0.5 y1 <- Intervals( c( .5, 1 - delta / 2 ) ) y2 <- Intervals( c( .25, 1, .75, 2 ) ) # Nominal interval_intersection( y1, y2 ) # Inner limit inner <- interval_intersection( contract( y1, delta, "relative" ), contract( y2, delta, "relative" ) ) # Outer limit outer <- interval_intersection( expand( y1, delta, "relative" ), expand( y2, delta, "relative" ) ) # The ambiguous set, corresponding to points which may or may not be in # the intersection -- depending on numerical values for endpoints # which are, with respect to relative difference, indistinguishable from # the nominal values. interval_difference( outer, inner )