Jason Stover <[EMAIL PROTECTED]> writes:
> I have a collection of small SAS data sets that I have been using to
> try to decipher the SAS data file format. I made some progress and
> have reached a more difficult task of figuring out how the actual
> numeric values are encoded.
I made a little headway on that fairly quickly. We can use Perl
to see how numeric values are encoded as IEEE doubles, e.g.:
[EMAIL PROTECTED]:~(0)$ perl -e 'print pack("d", 8.0)' | hd
00000000 00 00 00 00 00 00 20 40 |...... @|
00000008
[EMAIL PROTECTED]:~(0)$ perl -e 'print pack("d", 9.0)' | hd
00000000 00 00 00 00 00 00 22 40 |......"@|
00000008
[EMAIL PROTECTED]:~(0)$
Then, we can dump the differences between files that are supposed
to contain those values and look for them:
[EMAIL PROTECTED]:~/tmp/sas(0)$ diff -u <(hd
n_cases_1_float_9_lc_a.sas7bdat) <(hd n_cases_1_float_8_lc_a.sas7bdat) |grep
'22 40\|20 40'
-00000490 00 00 00 00 00 00 22 40 61 20 20 20 20 20 20 20 |......"@a
|
+00000490 00 00 00 00 00 00 20 40 61 20 20 20 20 20 20 20 |...... @a
|
There are other differences between these files but those really
stick out.
--
"Then, I came to my senses, and slunk away, hoping no one overheard my
thinking."
--Steve McAndrewSmith in the Monastery
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