Rmpfr (version 0.5-0)

mpfr-class: Class "mpfr" of Multiple Precision Floating Point Numbers

Description

"mpfr" is the class of Multiple Precision Floatingpoint numbers with Reliable arithmetic.

For the high-level user, "mpfr" objects should behave as standard R's numeric vectors, just with prespecified (typically high) precision.

Objects from the Class

Objects are typically created by mpfr(, precBits).

See Also

The "mpfrMatrix" class, which extends the "mpfr" one.

roundMpfr to change precision of an "mpfr" object; is.whole() etc.

Special mathematical functions such as some Bessel ones, e.g., jn; further, zeta(.) $(= \zeta(.))$, Ei() etc. Bernoulli numbers and the Pochhammer function pochMpfr.

Examples

## 30 digit precision
str(x <- mpfr(c(2:3, pi), prec = 30 * log2(10)))
x^2
x[1] / x[2] # 0.66666... ~ 30 digits

## indexing - as with numeric vectors
stopifnot(identical(x[2], x[[2]]),
	  ## indexing "outside" gives NA (well: "mpfr-NaN" for now):
	  is.na(x[5]),
	  ## whereas "[[" cannot index outside:
	  is(try(x[[5]]), "try-error"),
	  ## and only select *one* element:
	  is(try(x[[2:3]]), "try-error"))

## factorial() & lfactorial would work automagically via [l]gamma(),
## but factorial() additionally has an "mpfr" method which rounds
f200 <- factorial(mpfr(200, prec = 1500)) # need high prec.!
f200
as.numeric(log2(f200))# 1245.38 -- need precBits >~ 1246 for full precision

##--> see  factorialMpfr() for more such computations.

##--- "Underflow" **much** later -- exponents have 30(+1) bits themselves:

mpfr.min.exp2 <- - (2^30 + 1)
two <- mpfr(2, 55)
stopifnot(two ^ mpfr.min.exp2 == 0)
## whereas
two ^ (mpfr.min.exp2 * (1 - 1e-15))
## 2.38256490488795107e-323228497   ["typically"]

## Above, we mention {sort}, {order}, {quantile}, {rank}.
p <- mpfr(rpois(12, lambda=500), precBits=128)^10
if(FALSE)## FIXME
  stopifnot(all(diff(sort(p)) > 0))