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Fix 271 (#273)
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* fix _check_lons for datasets with 0 lon value

* Added a better decorator for checking date signatures

* Type checking fixes

* Docstring fixes
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@Zeitsperre
Zeitsperre authored Sep 23, 2019
1 parent e921601 commit 784896a
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Showing 3 changed files with 81 additions and 29 deletions.
2 changes: 2 additions & 0 deletions HISTORY.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,8 @@ History
* Updated subset.py to use date formatted strings ("%Y", "%Y%m" etc.) in temporal subsetting
* Clean-up of day-of-year resampling. Precipitation percentile threshold will work without a doy index.
* Addressed deprecations for xarray 0.13.0
* Added a decorator function that verifies validity and reformats subset calls using start_date or end_date signatures.
* Fixed a bug where 'lon' or 'lon_bounds' would return false values if either signatures were set to 0.

0.10-beta (2019-06-06)
----------------------
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14 changes: 14 additions & 0 deletions tests/test_subset.py
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Expand Up @@ -96,6 +96,20 @@ def test_time_simple(self):
np.testing.assert_array_equal(out.time.dt.year.max(), int(yr_ed))
np.testing.assert_array_equal(out.time.dt.year.min(), int(yr_st))

def test_time_dates_outofbounds(self):
da = xr.open_dataset(self.nc_poslons).tas
da["lon"] -= 360
yr_st = "1950"
yr_ed = "2099"

out = subset.subset_gridpoint(
da,
start_date="{yr_st}-01".format(yr_st=yr_st),
end_date="{yr_ed}-01".format(yr_ed=yr_ed),
)
np.testing.assert_array_equal(out.time.dt.year.min(), da.time.dt.year.min())
np.testing.assert_array_equal(out.time.dt.year.max(), da.time.dt.year.max())

def test_time_start_only(self):
da = xr.open_dataset(self.nc_poslons).tas
da["lon"] -= 360
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94 changes: 65 additions & 29 deletions xclim/subset.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
import datetime
import warnings
from typing import List
from typing import Union

import numpy as np
import xarray
Expand All @@ -8,7 +10,7 @@
__all__ = ["subset_bbox", "subset_gridpoint", "subset_time"]


def check_dates(func):
def check_date_signature(func):
def func_checker(*args, **kwargs):
"""
A decorator to reformat the deprecated `start_yr` and `end_yr` calls to subset functions and return
Expand Down Expand Up @@ -43,14 +45,60 @@ def func_checker(*args, **kwargs):
return func_checker


def check_lons(func):
def check_start_end_dates(func):
def func_checker(*args, **kwargs):
"""
A decorator to reformat user-specified lon values based on the lon dimensions of a supplied xarray
DataSet or DataArray. Returns a numpy array of reformatted `lon` or `lon_bnds` in kwargs
with min() and max() values.
A decorator to verify that start and end dates are valid in a time subsetting function.
"""
da = args[0]
if "start_date" not in kwargs:
# use string for first year only - .sel() will include all time steps
kwargs["start_date"] = da.time.min().dt.strftime("%Y").values
if "end_date" not in kwargs:
# use string for last year only - .sel() will include all time steps
kwargs["end_date"] = da.time.max().dt.strftime("%Y").values

try:
da.time.sel(time=kwargs["start_date"])
except KeyError:
warnings.warn(
'"start_date" not found within input date time range. Defaulting to minimum time step in '
"xarray object.",
Warning,
stacklevel=2,
)
kwargs["start_date"] = da.time.min().dt.strftime("%Y").values
try:
da.time.sel(time=kwargs["end_date"])
except KeyError:
warnings.warn(
'"end_date" not found within input date time range. Defaulting to maximum time step in '
"xarray object.",
Warning,
stacklevel=2,
)
kwargs["end_date"] = da.time.max().dt.strftime("%Y").values

if (
da.time.sel(time=kwargs["start_date"]).min()
> da.time.sel(time=kwargs["end_date"]).max()
):
raise ValueError("Start date is after end date.")

return func(*args, **kwargs)

return func_checker


def check_lons(func):
def func_checker(*args, **kwargs):
"""
A decorator to reformat user-specified "lon" or "lon_bnds" values based on the lon dimensions of a supplied
xarray DataSet or DataArray. Examines an xarray object longitude dimensions and depending on extent
(either -180 to +180 or 0 to +360), will reformat user-specified lon values to be synonymous with
xarray object boundaries.
Returns a numpy array of reformatted `lon` or `lon_bnds` in kwargs with min() and max() values.
"""
if "lon_bnds" in kwargs:
lon = "lon_bnds"
elif "lon" in kwargs:
Expand All @@ -63,24 +111,23 @@ def func_checker(*args, **kwargs):
kwargs[lon] = np.asarray(args[0].lon.min(), args[0].lon.max())
else:
kwargs[lon] = np.asarray(kwargs[lon])
if np.all(args[0].lon > 0) and np.any(kwargs[lon] < 0):
if np.all(args[0].lon >= 0) and np.any(kwargs[lon] < 0):
if isinstance(kwargs[lon], float):
kwargs[lon] += 360
else:
kwargs[lon][kwargs[lon] < 0] += 360
if np.all(args[0].lon < 0) and np.any(kwargs[lon] > 0):
if np.all(args[0].lon <= 0) and np.any(kwargs[lon] > 0):
if isinstance(kwargs[lon], float):
kwargs[lon] -= 360
else:
kwargs[lon][kwargs[lon] < 0] -= 360

return func(*args, **kwargs)

return func_checker


@check_lons
@check_dates
@check_date_signature
def subset_bbox(da, lon_bnds=None, lat_bnds=None, start_date=None, end_date=None):
"""Subset a datarray or dataset spatially (and temporally) using a lat lon bounding box and date selection.
Expand Down Expand Up @@ -115,8 +162,8 @@ def subset_bbox(da, lon_bnds=None, lat_bnds=None, start_date=None, end_date=None
Returns
-------
xarray.DataArray or xarray.DataSet
subsetted data array or dataset
Union[xarray.DataArray, xarray.DataSet]
Subsetted xarray.DataArray or xarray.DataSet
Examples
--------
Expand Down Expand Up @@ -239,7 +286,7 @@ def _check_desc_coords(coord, bounds, dim):


@check_lons
@check_dates
@check_date_signature
def subset_gridpoint(da, lon=None, lat=None, start_date=None, end_date=None):
"""Extract a nearest gridpoint from datarray based on lat lon coordinate.
Time series can optionally be subsetted by dates
Expand Down Expand Up @@ -273,8 +320,8 @@ def subset_gridpoint(da, lon=None, lat=None, start_date=None, end_date=None):
Returns
-------
xarray.DataArray or xarray.DataSet
Subsetted data array or dataset
Union[xarray.DataArray, xarray.DataSet]
Subsetted xarray.dataArray or xarray.DataSet
Examples
--------
Expand Down Expand Up @@ -336,6 +383,7 @@ def subset_gridpoint(da, lon=None, lat=None, start_date=None, end_date=None):
return da


@check_start_end_dates
def subset_time(da, start_date=None, end_date=None):
"""Subset input data based on start and end years
Expand All @@ -344,7 +392,7 @@ def subset_time(da, start_date=None, end_date=None):
Parameters
----------
da : xarray.DataArray or xarray.DataSet
da : Union[xarray.DataArray, xarray.DataSet]
Input data.
start_date : str
Start date of the subset.
Expand All @@ -357,8 +405,8 @@ def subset_time(da, start_date=None, end_date=None):
Returns
-------
xarray.DataArray or xarray.DataSet
Subsetted data array or dataset
Union[xarray.DataArray, xarray.DataSet]
Subsetted xarray.DataArray or xarray.DataSet
Examples
--------
Expand All @@ -378,18 +426,6 @@ def subset_time(da, start_date=None, end_date=None):
Notes
TODO add notes about different calendar types. Avoid "%Y-%m-31". If you want complete month use only "%Y-%m".
"""

if not start_date:
# use string for first year only - .sel() will include all time steps
start_date = da.time.min().dt.strftime("%Y").values
if not end_date:
# use string for last year only - .sel() will include all time steps
end_date = da.time.max().dt.strftime("%Y").values

if da.time.sel(time=start_date).min() > da.time.sel(time=end_date).max():
raise ValueError("Start date is after end date.")

return da.sel(time=slice(start_date, end_date))

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