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Merged
merged 2 commits into from
Jun 3, 2022
Merged

Convenience methods for time conversion #384

merged 2 commits into from
Jun 3, 2022

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bemoody
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@bemoody bemoody commented Jun 2, 2022

Add some convenience methods for converting between different representations of time:

  • frame number (represented as an integer or float)
  • elapsed time (represented as a timedelta)
  • absolute time (represented as a datetime)

For example, if I want to see the signals for MIMIC-III patient 44083, between 2112-05-04 20:00:00 and 2112-05-04 20:05:00, I might do this:

>>> rec_name = 'p044083-2112-05-04-19-50'
>>> pn_dir = 'mimic3wdb-matched/1.0/p04/p044083'
>>> header = wfdb.rdheader(rec_name, pn_dir=pn_dir)
>>> dt1 = datetime.datetime.fromisoformat('2112-05-04 20:00:00')
>>> dt2 = datetime.datetime.fromisoformat('2112-05-04 20:05:00')
>>> start = round(header.get_frame_number(dt1))
>>> end = round(header.get_frame_number(dt2))
>>> chunk = wfdb.rdrecord(rec_name, pn_dir=pn_dir, sampfrom=start, sampto=end)
>>> wfdb.plot_wfdb(chunk)

Benjamin Moody added 2 commits June 2, 2022 15:34
BaseRecord: add time conversion methods.
6c135b1 
These methods can be used to convert between three different
representations of time:

- frame number (i.e., an index into the p_signal or d_signal array)

- elapsed time in microseconds, represented by a datetime.timedelta
  object

- absolute date and time, represented by a datetime.datetime object

Each of these methods will accept any of these three representations
as an argument, and convert into the specified representation.

For example, using record 100 (which has a frame frequency of 360 Hz):

    >>> r = wfdb.rdrecord('sample-data/100')
    >>> r.get_elapsed_time(180)
    datetime.timedelta(microseconds=500000)
    >>> r.get_frame_number(datetime.timedelta(seconds=0.5))
    180.0
Add test cases for time conversion functions.
f224b0f 
Test that the get_frame_number, get_elapsed_time, and
get_absolute_time methods work correctly, for both Record and
MultiRecord objects.
tompollard
tompollard approved these changes Jun 3, 2022
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Looks good to me!

@tompollard tompollard merged commit 84cbefb into main Jun 3, 2022
@tompollard tompollard deleted the time-conversion branch June 3, 2022 17:35
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@bemoody @tompollard