In R software
a <- 123456789123456789123456789
sprintf("%27f",a)
#[1] "123456789123456791337762816.000000"
I got the wrong answer. I want exact a value.
Why is the system showing the wrong value of a?
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Also check [here](http://stackoverflow.com/questions/32339636/long-numbers-as-a-character-string) – akrun Sep 03 '15 at 06:48
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As explained in [this comment](http://stackoverflow.com/questions/40419024/is-there-a-way-to-display-frank-nelson-coles-factors-of-267-%e2%88%92-1-correctly-with#comment68089039_40419024) (under a duplicate question), do not forget to pass a character when using `gmp::as.bigz()`. – Paul Rougieux Nov 04 '16 at 10:32
1 Answers
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The reason you're not getting your exact value of a is that R is storing it as a double instead of as an integer. Because a is very large, there is some rounding that takes place when you assign a.
Normally to store things as integers you would use L at the end of the numbers; something like:
a <- 12L
class(a)
# [1] "integer"
However your number is too large for a standard integer in R, and you're forced to use the double representation:
a <- 123456789123456789123456789L
# Warning message:
# non-integer value 123456789123456789123456789L qualified with L; using numeric value
class(a)
# [1] "numeric"
You will need multiple precision to exactly store an integer this large. One option would be the gmp package:
library(gmp)
a<-as.bigz("123456789123456789123456789")
a
# Big Integer ('bigz') :
# [1] 123456789123456789123456789
Other options for multi-precision arithmetic are available under the "Multi-Precision Arithmetic and Symbolic Mathematics" subheading of the numerical mathematics CRAN task view.
josliber
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@aarthi you should store each as a bigz and then multiply; something like `prod(as.bigz(c(2, 3, 7, 43, 1807, 3263443)))` – josliber Sep 03 '15 at 06:58
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factorize( 113423713055421844361000443) and factorize(113423713055421845118910464) have the same answer what i do? – aarthi Sep 03 '15 at 08:29