[SciPy-User] Matching date lists

Cumberland, Burly Burly.Cumberland@coherent....
Thu Feb 4 08:14:11 CST 2010


Hi,

 

I have several datasets which are linked to date/timestamps. I import
these in and convert all the dates to python datetime objects. So for
instance I might have something like

 

Array of datetime objects with an array of data values associated with
it, say A.

Another array of datetime objects with several arrays of data values
associated, say B, C and D.

 

The time stream is not continuous, i.e. there may be 5-6 days data then
nothing for a day then 10 days data. While some of the arrays are at
regular sample intervals (frequency) at least one of them has data
generated at a higher frequency but with no fixed period. Ideally I
would like to associate the closest measurement from this list with the
datetime stamp from the first list. Thus if I have

 

array([2009-12-23 13:57:16, 2009-12-23 13:58:15, 2009-12-23 13:59:14,

      2009-12-23 14:00:14, 2009-12-23 14:01:13, 2009-12-23 14:02:13,

      2009-12-23 14:03:13, 2009-12-23 14:04:12, 2009-12-23 14:05:12,

      2009-12-23 14:06:12], dtype=object)

 

and

 

array([2009-12-23 13:57:21, 2009-12-23 13:57:28, 2009-12-23 13:57:37,

      2009-12-23 13:57:44, 2009-12-23 13:57:53, 2009-12-23 13:58:02,

      2009-12-23 13:58:09, 2009-12-23 13:58:17, 2009-12-23 13:58:25,

      2009-12-23 13:58:33], dtype=object)

 

I'd like to tie my values for the 1st and 8th values from the second
array to the first two values from the first array (assuming I'm happy
that the data is taken within 5 seconds of each other). Thus I'd mask or
disregard all the data in the second array set (B, C and D) that isn't
measured within a reasonable time period of the first.

 

Clearly I could write a loop and do comparisons and then copy the data
or pop it. The problem is there's a quarter of a million items in the
data set at the minute and it continues to grow. So I was wondering if
anyone can recommend a method or module, I'd a brief look at timeseries
and pandas but neither appears to have a tool which resolves this for
me.

 

Any suggestions welcome.

 

Regards,

Burly.

 

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