Built-in function for extracting mantissa and exponent of a numeric

Dear all,

Given a number

x<-1.234e12

is there a built-in function for extracting 1.234 and 12 ?

No, because that is not how the number is stored (and in fact the value 
stored is a binary fraction with a slightly different value).

The following "hack" seems clumpsy:

format() is doing a lot of work to produce a decimal approximation to 
'x', including choosing the precision.

It is not clear what you want: if you merely want to express x as a*10^b 
for 1 <= a < 10 then

b <- floor(log10(x))
a <- x/10^b

does the job (but might get values of a very slightly less than 1 or 
above 10, so if you care this might need checking and refinement).

a<-strsplit(format(x, scientific=T),"e")[[1]]
a

[1] "1.234" "+12"

as.numeric(a[1])

[1] 1.234

as.integer(a[2])

[1] 12

Regards
S?ren

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Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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