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362 lines
11 KiB
362 lines
11 KiB
from __future__ import (absolute_import, division, print_function) |
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from .constants import Constants, ConversionFactors |
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def _apply_conv_fact(var, vartype, var_unit, dest_unit): |
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"""Return the variable converted to different units using a conversion |
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factor. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable. |
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vartype (:obj:`str`): The type of variable. Choices are: 'wind', |
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'pressure', 'temp', or 'height'. |
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var_unit (:obj:`str`): The variable's current units. |
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dest_unit (:obj:`str`): The desired units. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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the desired units. |
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""" |
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if var_unit == dest_unit: |
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return var |
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# Note, case where var_unit and dest_unit are base unit, should be |
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# handled above |
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if var_unit == _BASE_UNITS[vartype]: |
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return var*(_CONV_FACTORS[vartype]["to_dest"][dest_unit]) |
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else: |
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if dest_unit == _BASE_UNITS[vartype]: |
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return var*(_CONV_FACTORS[vartype]["to_base"][var_unit]) |
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else: |
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return var*(_CONV_FACTORS[vartype]["to_base"][var_unit] * |
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_CONV_FACTORS[vartype]["to_dest"][dest_unit]) |
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def _to_kelvin(var, var_unit): |
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"""Return the variable in Kelvin. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable. |
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var_unit (:obj:`str`): The variable's current units. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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Kelvin. |
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""" |
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if var_unit == "c": |
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return var + Constants.CELKEL |
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elif var_unit == "f": |
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return (var - 32.0) * (5.0/9.0) + Constants.CELKEL |
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def _k_to_c(var): |
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"""Return the variable in Celsius. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable in units of Kelvin. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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Celsius. |
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""" |
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return var - Constants.CELKEL |
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def _k_to_f(var): |
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"""Return the variable in Fahrenheit. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable in units of Kelvin. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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Fahrenheit. |
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""" |
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return 1.8 * _k_to_c(var) + 32.0 |
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def _apply_temp_conv(var, var_unit, dest_unit): |
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"""Return the variable converted to different units using a temperature |
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conversion algorithm. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable. |
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var_unit (:obj:`str`): The variable's current units. |
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dest_unit (:obj:`str`): The desired units. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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the desired units. |
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""" |
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if dest_unit == var_unit: |
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return var |
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if var_unit != _BASE_UNITS["temp"]: |
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tk = _to_kelvin(var, var_unit) |
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if dest_unit == _BASE_UNITS["temp"]: |
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return tk |
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else: |
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return (_TEMP_CONV_METHODS[dest_unit])(tk) |
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else: |
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return (_TEMP_CONV_METHODS[dest_unit])(var) |
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# A mapping of unit names to their dictionary key names |
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_UNIT_ALIASES = {"mps": "m s-1", |
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"m/s": "m s-1", |
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"ms-1": "m s-1", |
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"meters_per_second": "m s-1", |
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"metres_per_second": "m s-1", |
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"knots": "kt", |
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"knot": "kt", |
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"kts": "kt", |
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"kn": "kt", |
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"miles_per_hour": "mi h-1", |
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"mih-1": "mi h-1", |
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"mph": "mi h-1", |
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"mi/h": "mi h-1", |
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"kmph": "km h-1", |
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"kmh-1": "km h-1", |
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"km/h": "km h-1", |
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"kilometers_per_hour": "km h-1", |
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"kilometres_per_hour": "km h-1", |
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"ft/s": "ft s-1", |
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"ft/sec": "ft s-1", |
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"fps": "ft s-1", |
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"fs-1": "ft s-1", |
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"feet_per_second": "ft s-1", |
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"pascal": "pa", |
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"pascals": "pa", |
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"hecto_pascal": "hpa", |
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"hecto_pascals": "hpa", |
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"millibar": "mb", |
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"millibars": "mb", |
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"mbar": "mb", |
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"kelvin": "k", |
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"degree_kelvin": "k", |
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"degrees_kelvin": "k", |
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"degree_k": "k", |
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"degrees_k": "k", |
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"degreek": "k", |
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"degreesk": "k", |
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"degk": "k", |
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"degsk": "k", |
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"deg_k": "k", |
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"degs_k": "k", |
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"deg k": "k", |
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"degs k": "k", |
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"celsius": "c", |
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"degree_celsius": "c", |
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"degrees_celsius": "c", |
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"degree_c": "c", |
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"degrees_c": "c", |
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"degreec": "c", |
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"degreesc": "c", |
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"degc": "c", |
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"degsc": "c", |
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"deg_c": "c", |
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"degs_c": "c", |
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"deg c": "c", |
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"degs c": "c", |
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"fahrenheit": "f", |
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"degree_fahrenheit": "f", |
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"degrees_fahrenheit": "f", |
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"degree_f": "f", |
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"degrees_f": "f", |
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"degreef": "f", |
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"degreesf": "f", |
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"degf": "f", |
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"degsf": "f", |
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"deg_f": "f", |
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"degs_f": "f", |
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"deg f": "f", |
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"degs f": "f", |
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"meter": "m", |
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"meters": "m", |
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"metre": "m", |
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"metres": "m", |
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"kilometer": "km", |
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"kilometers": "km", |
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"dekameter": "dm", |
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"dekameters": "dm", |
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"decameter": "dm", |
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"decameters": "dm", |
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"dekametre": "dm", |
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"dekametres": "dm", |
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"decametre": "dm", |
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"decametres": "dm", |
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"dam": "dm", |
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"dkm": "dm", |
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"feet": "ft", |
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"foot": "ft", |
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"mile": "mi", |
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"miles": "mi" |
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} |
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# A mapping of unit types to the avaible units |
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_VALID_UNITS = {"wind": ["m s-1", "kt", "mi h-1", "km h-1", "ft s-1"], |
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"pressure": ["pa", "hpa", "mb", "torr", "mmhg", "atm"], |
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"temp": ["k", "f", "c"], |
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"height": ["m", "km", "dm", "ft", "mi"] |
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} |
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# Conversion factor map for wind from base units |
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_WIND_BASE_FACTORS = {"kt": ConversionFactors.MPS_TO_KTS, |
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"km h-1": ConversionFactors.MPS_TO_KMPH, |
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"mi h-1": ConversionFactors.MPS_TO_MPH, |
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"ft s-1": ConversionFactors.MPS_TO_FPS |
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} |
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# Conversion factor map to base units |
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_WIND_TOBASE_FACTORS = {"kt": 1.0/ConversionFactors.MPS_TO_KTS, |
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"km h-1": 1.0/ConversionFactors.MPS_TO_KMPH, |
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"mi h-1": 1.0/ConversionFactors.MPS_TO_MPH, |
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"ft s-1": 1.0/ConversionFactors.MPS_TO_FPS |
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} |
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# Conversion factor map for pressure from base units |
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_PRES_BASE_FACTORS = {"hpa": ConversionFactors.PA_TO_HPA, |
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"mb": ConversionFactors.PA_TO_HPA, |
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"torr": ConversionFactors.PA_TO_TORR, |
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"mmhg": ConversionFactors.PA_TO_MMHG, |
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"atm": ConversionFactors.PA_TO_ATM |
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} |
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# Conversion factor map for pressure to base units |
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_PRES_TOBASE_FACTORS = {"hpa": 1.0/ConversionFactors.PA_TO_HPA, |
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"mb": 1.0/ConversionFactors.PA_TO_HPA, |
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"torr": 1.0/ConversionFactors.PA_TO_TORR, |
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"mmhg": 1.0/ConversionFactors.PA_TO_MMHG, |
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"atm": 1.0/ConversionFactors.PA_TO_ATM |
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} |
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# Conversion factor map for height from base units |
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_HEIGHT_BASE_FACTORS = {"km": ConversionFactors.M_TO_KM, |
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"dm": ConversionFactors.M_TO_DM, |
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"ft": ConversionFactors.M_TO_FT, |
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"mi": ConversionFactors.M_TO_MILES |
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} |
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# Conversion factor map for height to base units |
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_HEIGHT_TOBASE_FACTORS = {"km": 1.0/ConversionFactors.M_TO_KM, |
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"dm": 1.0/ConversionFactors.M_TO_DM, |
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"ft": 1.0/ConversionFactors.M_TO_FT, |
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"mi": 1.0/ConversionFactors.M_TO_MILES |
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} |
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# Mapping of unit type to base unit type |
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_BASE_UNITS = {"wind": "m s-1", |
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"pressure": "pa", |
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"temp": "k", |
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"height": "m" |
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} |
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# A mapping of unit type to a mapping of to/from base conversion factors |
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_CONV_FACTORS = {"wind": {"to_dest": _WIND_BASE_FACTORS, |
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"to_base": _WIND_TOBASE_FACTORS}, |
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"pressure": {"to_dest": _PRES_BASE_FACTORS, |
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"to_base": _PRES_TOBASE_FACTORS}, |
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"height": {"to_dest": _HEIGHT_BASE_FACTORS, |
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"to_base": _HEIGHT_TOBASE_FACTORS} |
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} |
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# A mapping of temperature type to the conversion function |
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_TEMP_CONV_METHODS = {"c": _k_to_c, |
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"f": _k_to_f |
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} |
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def dealias_and_clean_unit(unit): |
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"""Return the properly cleaned and dealiased unit name. |
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Args: |
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unit (:obj:`str`): The unit name. |
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Returns: |
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:obj:`str`: A unit name suitable for dictionary key lookups. |
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""" |
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cleaned_unit = " ".join(unit.lower().split()) |
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dealiased = _UNIT_ALIASES.get(cleaned_unit, None) |
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return cleaned_unit if dealiased is None else dealiased |
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def check_units(unit, unit_type): |
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"""Raise an exception if the unit name is invalid. |
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Args: |
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unit (:obj:`str`): The unit name. |
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unit_type (:obj:`str`): The type of unit. |
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Returns: |
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None |
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Raises: |
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:class:`ValueError`: Raised when the unit name is invalid. |
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""" |
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u_cleaned = dealias_and_clean_unit(unit) |
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if u_cleaned not in _VALID_UNITS[unit_type]: |
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raise ValueError("invalid unit type '{}'".format(unit)) |
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def do_conversion(var, vartype, var_unit, dest_unit): |
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"""Return the variable converted to different units. |
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Args: |
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var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A |
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variable. |
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vartype (:obj:`str`): The type of variable. Choices are: 'wind', |
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'pressure', 'temp', or 'height'. |
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var_unit (:obj:`str`): The variable's current units. |
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dest_unit (:obj:`str`): The desired units. |
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Returns: |
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:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in |
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the desired units. |
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""" |
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u_cleaned = dealias_and_clean_unit(dest_unit) |
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if vartype != "temp": |
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return _apply_conv_fact(var, vartype, var_unit.lower(), u_cleaned) |
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else: |
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return _apply_temp_conv(var, var_unit.lower(), u_cleaned)
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