This question already has answers here:
Why are floating point numbers inaccurate?
(5 answers)
Why are these numbers not equal?
(6 answers)
Closed last month.
Suppose I have big numbers such as this: 10.295.419.305.791.578.917.358.173.519.057.891.283.897.623.986
library(gmp)
as.bigz(10295419305791578917358173519057891283897623986)
And this might outputs:
Big Integer ('bigz') :
[1] 10295419305791579051260295299235939155628261376
Visually the value 10.295.419.305.791.579.051.260.295.299.235.939.155.628.261.376 is already different compared the input (begins after 15 digits from beginning)
My question: are there any explanation to this? is it because of numeric error before it being converted to big integer?
While I still find a way to get the accurate value by adding quotes.. such as:
as.bigz("10295419305791578917358173519057891283897623986")
Big Integer ('bigz') :
[1] 10295419305791578917358173519057891283897623986
Related
This question already has answers here:
Why (1UL <<53) plus 1.0 does not equal to itself?
(2 answers)
Is floating point math broken?
(31 answers)
Closed 1 year ago.
Why is it that when I put this equation in matlab it equals 0 but when I do (2^52+1) -2^52 it gives me 1, aren't they the same equation. I think I kind of understand how 64bit float can't represent odd numbers past 2^53-1 but these numbers are not even close to that
There are 2^52 double precision numbers between 2^52 and 2^53-1 which the sqrt function maps to (approximately) the interval [2^26, sqrt(2)*2^26]. The latter contains just 2^52/sqrt(2) numbers, which means a lot of numbers x must map to the same sqrt(x).
This question already has answers here:
Is floating point math broken?
(31 answers)
Why are these numbers not equal?
(6 answers)
Closed 5 years ago.
options(digits = 18)
x <- 0.127272727272727287
str(x)
# num 0.127
x
#[1] 0.127272727272727287
as.character(x)
#[1] "0.127272727272727"
as.numeric(as.character(x))
[1] 0.12727272727272701
Where does the 01 come from? What's going on here?
This is hinted at in the help page ?options when you look at the section on digits. You can set the number of digits to any number up to 22, but that does not mean that R will accurately represent that many digits. R uses
IEEE double-precision. Wikipedia tells us that this representation has
Sign bit: 1 bit
Exponent: 11 bits
Significand precision: 53 bits (52 explicitly stored)
So R is storing numbers to log(2^53, 10) = 15.95459 decimal digits accuracy. Anything you get beyond that is luck.
This question already has answers here:
Why are these numbers not equal?
(6 answers)
Closed 5 years ago.
When I to convert large numbers formatted as character strings to numeric R changes the last digits. This also happens when I pass it the number itself.
For example:
> options(scipen = 999)
> as.numeric("3411190080123000215")
[1] 3411190080123000320
> as.numeric(3411190080123000215)
[1] 3411190080123000320
This also happens when I use other numeric functions:
> floor(3411190080123000215)
[1] 3411190080123000320
Could this be an issue with my settings?
Thank you!!
The issue is that you are not actually using integers, you are using floats.
x <- as.numeric("3411190080123000215")
is.integer(x)
However, your number is too large to be stored as an integer anyway. Check out the gmp R package for arbitrarily large integers.
This question already has an answer here:
R floating point number precision being lost on coversion from character
(1 answer)
Closed 7 years ago.
How do I retain the full 16 digit precision when coercing a text to numeric in R?
My attempt below does not appear to do this...
x<-"0.501288104715059"
x<-as.double(x)
x
[1] 0.5012881
[Note this is similar to a previously asked question using as.numeric to convert a character to number but his question refers to the case of using as.double to convert a character to a number]
The code in fact does work - I just needed to set the number of digits to be displayed
x<-"0.501288104715059"
x<-as.double(x)
options(digits=16)
x
[1] 0.501288104715059
Might be useful to somebody else
This question already has answers here:
Controlling number of decimal digits in print output in R
(4 answers)
Closed 9 years ago.
I am trying to have sum of two values in R with 6 decimal places but it only returns with 5.
85.85+0.01302778
# [1] 85.86303
I tried
round(85.85+0.01302778,6)
but it does not work.
Actually sum(85.85,0.01302778) gives only 5 decimals and I did not find any scope of decimal places in ?sum.
Any suggestions
Try this to get 6 digits:
> options(digits=8)
> 85.85+0.01302778
[1] 85.863028