On Wed, 31 Mar 2004 12:24:38 -0500, Stephane DRAY
<[EMAIL PROTECTED]> wrote :
>Hello list,
>I have used scan function to import data into R. I have done some analysis
>and find strange results. I have found my problem : when importing data
>with scan, this can slightly modify the data :
>
> > write(c(0.251,3.399,-0.481,0.266),"essai.txt")
> > scan("essai.txt")
>Read 4 items
>[1] 0.251 3.399 -0.481 0.266
> > print(scan("essai.txt"),17)
>Read 4 items
>[1] 0.25100000000000000 3.39900000000000000
>-0.48099999999999998 0.26600000000000001
>
>
>
>Is it normal ? Is it a bug ?
I think it's normal. Floating point formats aren't exact except for
fractions with only powers of 2 in the denominator. There is no way
to represent any of your values in the formats that R uses without
slight errors.
I do notice one oddity in the print routines in R:
> x<-scan()
1: 0.266
2: 0.251
3:
Read 2 items
> print(x,17)
[1] 0.26600000000000001 0.25100000000000000
> x<-scan()
1: 0.266
2:
Read 1 items
> print(x,17)
[1] 0.266
I don't know why the second print() prints 0.266 differently from the
first one. (This is in the 1.9.0 beta in Windows).
Duncan Murdoch
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