zapsmall {base}R Documentation

Rounding of Numbers: Zapping Small Ones to Zero

Description

zapsmall determines a digits argument dr for calling round(x, digits = dr) such that values close to zero (compared with the maximal absolute value in the vector) are ‘zapped’, i.e., replaced by 0. digits = Inf keeps the full precision, returning x unchanged.

Usage

zapsmall(x, digits = getOption("digits"),
         mFUN = function(x, ina) max(abs(x[!ina])),
         min.d = 0L)

Arguments

x

a numeric or complex vector or any R number-like object which has a round method and basic arithmetic methods including log10().

digits

integer indicating the precision to be used.

mFUN

a function(x, ina) of the numeric (or complex) x and the logical ina := is.na(x) returning a positive number in the order of magnitude of the maximal abs(x) value. The default is back compatible but not robust, and e.g., not very useful when x has infinite entries.

min.d

an integer specifying the minimal number of digits to use in the resulting round(x, digits=*) call when mFUN(*) > 0. Using min.d = -324 or smaller provides scale invariance, whereas the default min.d = 0 is back compatible with S and R versions before 4.4.0 where, it was implicitly hardwired to 0 with the intuition that e.g., 4 should never be zapped to code0.

References

Chambers JM (1998). Programming with Data. Springer, New York. ISBN 978-0-387-98503-9.

Examples

x2 <- pi * 100^(-2:2)/10
   print(  x2, digits = 4)
zapsmall(  x2) # automatic digits
zapsmall(  x2,   digits = 4) # 0 0 0.3 ...
zapsmall(1e6*x2, digits = 4) #  no zeros (*not* scale invariant)
zapsmall(1e6*x2, digits = 4, min.d = -324) # 0 0 .. *is* scale inv.
zapsmall(c(x2, Inf)) # round()s to integer, as min.d = 0
zapsmall(c(x2, Inf), min.d=-Inf) # 0 0 .. 0 Inf -- everything  is small wrt  Inf

(z <- exp(1i*0:4*pi/2))
zapsmall(z)

zapShow <- function(x, ...) rbind(orig = x, zapped = zapsmall(x, ...))
zapShow(x2)

## using a *robust* mFUN
mF_rob <- function(x, ina) boxplot.stats(x, do.conf=FALSE)$stats[5]
## a simpler robust one:
mF_Q3  <- function(x, ina) { x <- abs(x[is.finite(x)])
    if(length(x <- x[x > 0])) quantile(x, 3/4, names=FALSE) else 0 }
## at least "protect from Inf":
mF_mxF <- function(x, ina) max(abs(x[is.finite(x)]))
## with robust mFUN(), 'Inf' is no longer distorting the picture:
zapShow(c(x2, Inf), mFUN = mF_Q3) # no zapping
zapShow(c(x2, Inf), mFUN = mF_Q3, min.d = -5) # the same
zapShow(c(x2, Inf), mFUN = mF_Q3, min.d = -324) #   same
zapShow(c(x2, 9999), mFUN = mF_Q3) # zap 1st
zapShow(c(x2, 9999), mFUN = mF_Q3, min.d = 3) # the same
zapShow(c(x2, 9999), mFUN = mF_Q3, min.d = -324)# ditto
zapShow(c(x2, 9999), mFUN = mF_Q3, min.d = 8) #  no zap

zapShow(c(x2, Inf), mFUN = mF_mxF) # no zapping
zapShow(c(x2, Inf), mFUN = mF_mxF, min.d = -5) # the same
zapShow(c(x2, Inf), mFUN = mF_mxF, min.d = -324) #   same
zapShow(c(x2, 9999), mFUN = mF_mxF)
zapShow(c(x2, 9999), mFUN = mF_mxF, min.d = 3) # the same
zapShow(c(x2, 9999), mFUN = mF_mxF, min.d = -324)# ditto
zapShow(c(x2, 9999), mFUN = mF_mxF, min.d = 8) # small diff

zapShow(c(x2, Inf), mFUN = mF_rob)
zapShow(c(x2, Inf), mFUN = mF_rob, min.d = -5) # the same
zapShow(c(x2, 9999), mFUN = mF_rob) # same *rounding* as w/ Inf
zapShow(c(x2, 9999), mFUN = mF_rob, min.d = 3) # the same
zapShow(c(x2, 9999), mFUN = mF_rob, min.d = 8) # small diff
[Package base version 4.6.0 Index]