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70 lines
2.4 KiB
ReStructuredText
70 lines
2.4 KiB
ReStructuredText
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Derived Measurements
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=====================
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The ``DerivedMeasurements`` API provides a consistent way of performing post
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processing on a provided :class:`MeasurementCsv` file.
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Example
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-------
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The following example shows how to use an implementation of a
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:class:`DerivedMeasurement` to obtain a list of calculated ``Measurements``.
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.. code-block:: ipython
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# Import the relevant derived measurement module
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# in this example the derived energy module is used.
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In [1]: from devlib import DerivedEnergyMeasurements
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# Obtain a MeasurementCsv file from an instrument or create from
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# existing .csv file. In this example an existing csv file is used which was
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# created with a sampling rate of 100Hz
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In [2]: from devlib import MeasurementsCsv
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In [3]: measurement_csv = MeasurementsCsv('/example/measurements.csv', sample_rate_hz=100)
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# Process the file and obtain a list of the derived measurements
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In [4]: derived_measurements = DerivedEnergyMeasurements.process(measurement_csv)
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In [5]: derived_measurements
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Out[5]: [device_energy: 239.1854075 joules, device_power: 5.5494089227 watts]
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API
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---
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Derived Measurements
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~~~~~~~~~~~~~~~~~~~~
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.. class:: DerivedMeasurements()
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The ``DerivedMeasurements`` class is an abstract base for implementing
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additional classes to calculate various metrics.
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.. method:: DerivedMeasurements.process(measurement_csv)
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Returns a list of :class:`Measurement` objects that have been calculated.
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Available Derived Measurements
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-------------------------------
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.. class:: DerivedEnergyMeasurements()
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The ``DerivedEnergyMeasurements`` class is used to calculate average power and
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cumulative energy for each site if the required data is present.
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The calculation of cumulative energy can occur in 3 ways. If a
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``site`` contains ``energy`` results, the first and last measurements are extracted
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and the delta calculated. If not, a ``timestamp`` channel will be used to calculate
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the energy from the power channel, failing back to using the sample rate attribute
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of the :class:`MeasurementCsv` file if timestamps are not available. If neither
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timestamps or a sample rate are available then an error will be raised.
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.. method:: DerivedEnergyMeasurements.process(measurement_csv)
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Returns a list of :class:`Measurement` objects that have been calculated for
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the average power and cumulative energy for each site.
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