Two dimensional regexp matching?
Benjamin Goldberg
goldbb2 at earthlink.net
Sun Jul 28 01:07:00 EDT 2002
Paddy wrote:
>
> We already have the re module for regular expression matching on a string.
>
> I am looking for pointers to references/algorithms for regular
> expression matching for files of tabular data, i.e.
>
> Table definition
> ================
> 1) Samples from one point in the system
> appears in a column of the table.
> 2) Samples encoded as characters
> 3) All points in the system are sampled at the
> same time to produce successive rows of the table
>
> So a system sampled at two points in successively may produce the
> following file:
>
> GH
> DF
> AS
> QW
> FF
> SD
>
> I want to be able to do regular expression type searches within the
> file. Things like
> Where can I find
> point1 == (D or G) then point2 == W within three samples
> and
> where the next sample of point2 != the earlier sample of point1?
Hmm...
To match just the first part /[DG].\n(?:..\n){0,2}.W\n/ might do it.
And with that other requirement: /([DG]).\n(?:..\n){0,2}.W\n.(?!=\1)./
> That was a small example, in reality there is usually hundreds of
> points and tens of thousands of samples in multi-megabyte files but
The problem isn't in the size of the data (or at least, not *just* in
the size of the data), but in the complexity of the regular expressions.
> I'd first like to see if anyone else has considered this kind of 'two
> dimensional regexp matching'
>
> Note: I DO NOT have queries in the date on sample points. The queries
> will always be "Find the range of sample times in which 'this'
> occurs".
>
> I have tried Google but without success - I don't know enough to think
> of a suitable search phrase, or, (much less likely), Google doesn't
> have it ;-)
>
> Thanks in advance, Paddy.
--
tr/`4/ /d, print "@{[map --$| ? ucfirst lc : lc, split]},\n" for
pack 'u', pack 'H*', 'ab5cf4021bafd28972030972b00a218eb9720000';
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