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