[Rd] Precision of function mean,bug?

[peter dalgaard]

Expected, see FAQ 7.31.

You just can't trust == on FP operations. Notice also

> a2=(z[idx]+x[idx]+y[idx])/3
> a2==a
[1] FALSE
> a2==b
[1] TRUE

-pd

> On 20 May 2020, at 12:40 , Morgan Morgan <morgan.emailbox using gmail.com> wrote:
> 
> Hello R-dev,
> 
> Yesterday, while I was testing the newly implemented function pmean in
> package kit, I noticed a mismatch in the output of the below R expressions.
> 
> set.seed(123)
> n=1e3L
> idx=5
> x=rnorm(n)
> y=rnorm(n)
> z=rnorm(n)
> a=(x[idx]+y[idx]+z[idx])/3
> b=mean(c(x[idx],y[idx],z[idx]))
> a==b
> # [1] FALSE
> 
> For idx= 1, 2, 3, 4 the last line is equal to TRUE. For 5, 6 and many
> others the difference is small but still.
> Is that expected or is it a bug?
> 
> Thank you
> Best Regards
> Morgan Jacob
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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