What I'm using:
R version 3.0.1 (2013-05-16) -- "Good Sport"
Copyright (C) 2013 The R Foundation for Statistical Computing
Platform: x86_64-unknown-linux-gnu (64-bit)
According to some docs, options(digits) controls numerical precision in
output of write.table(). I'm using the default value for digits:
getOption("digits")
[1] 7
I have a bunch of numbers in a data frame that are only a few digits to
the right of the decimal:
data[c(94,120), c(18,20,21)]
V18 V20 V21
94 0.008 0.008 0.000064
120 0.023 0.023 0.000529
I write the data to a file:
write.table(data, file="data.txt", sep="\t", row.names=F, col.names=F)
Then I look at those same values and this is what I see:
$ gawk -F'\t' 'NR==94 || NR==120 {print $18,$20,$21}' data.txt
0.00800000000000001 0.00800000000000001 6.40000000000001e-05
0.0229999999999999 0.0229999999999999 0.000528999999999996
This is the weird thing: Only those two records get the long, annoyingly
"precise" 17-digit numbers. Other records look like this:
0.052 1.052 1.106704
0.178 0.178 0.031684
I understand that binary representations won't reflect decimal
representations precisely, etc., but why do I get this junk for only two
records out of 197 records? Records that contain only integral values
can't get it wrong, but the other 30 of 32 records with decimals look fine
-- see below.
Also, if precision should be to 7 digits, why am I getting 17 digits for
exactly two of the records? Why does this happen for all three numbers in
those two records?
If you think this is a bug that I should report elsewhere, let me know.
Thanks.
Mike
$ gawk -F'\t' '{print $18,$20,$21}' data.txt | grep -F .
0.944 0.944 0.891136
0.885 1.885 3.553225
0.052 1.052 1.106704
0.178 0.178 0.031684
1.996 1.996 3.984016
0.86 1.86 3.4596
0.765 1.765 3.115225
0.986 1.986 3.944196
0.998 0.998 0.996004
0.998 0.998 0.996004
0.956 0.956 0.913936
0.99 1.99 3.9601
0.00800000000000001 0.00800000000000001 6.40000000000001e-05
0.99 0.99 0.9801
0.0229999999999999 0.0229999999999999 0.000528999999999996
0.938 0.938 0.879844
0.034 1.034 1.069156
0.86 1.86 3.4596
0.911 1.911 3.651921
0.971 0.971 0.942841
0.994 0.994 0.988036
0.418 0.418 0.174724
0.805 1.805 3.258025
0.996 1.996 3.984016
0.998 1.998 3.992004
0.623 1.623 2.634129
0.998 0.998 0.996004
1.628 1.628 2.650384
0.981 0.981 0.962361
0.998 0.998 0.996004
1.676 1.676 2.808976
0.986 1.986 3.944196
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