You can run this notebook in a live session or view it on Github.
Visualization Gallery¶
This notebook shows common visualization issues encountered in Xarray.
[1]:
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import xarray as xr
%matplotlib inline
Load example dataset:
[2]:
ds = xr.tutorial.load_dataset('air_temperature')
---------------------------------------------------------------------------
FileNotFoundError Traceback (most recent call last)
<ipython-input-2-15c698672cac> in <module>
----> 1 ds = xr.tutorial.load_dataset('air_temperature')
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/tutorial.py in load_dataset(*args, **kwargs)
111 open_dataset
112 """
--> 113 with open_dataset(*args, **kwargs) as ds:
114 return ds.load()
115
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/tutorial.py in open_dataset(name, cache, cache_dir, github_url, branch, **kws)
76 # May want to add an option to remove it.
77 if not _os.path.isdir(longdir):
---> 78 _os.mkdir(longdir)
79
80 url = "/".join((github_url, "raw", branch, fullname))
FileNotFoundError: [Errno 2] No such file or directory: '/sbuild-nonexistent/.xarray_tutorial_data'
Multiple plots and map projections¶
Control the map projection parameters on multiple axes
This example illustrates how to plot multiple maps and control their extent and aspect ratio.
For more details see this discussion on github.
[3]:
air = ds.air.isel(time=[0, 724]) - 273.15
# This is the map projection we want to plot *onto*
map_proj = ccrs.LambertConformal(central_longitude=-95, central_latitude=45)
p = air.plot(transform=ccrs.PlateCarree(), # the data's projection
col='time', col_wrap=1, # multiplot settings
aspect=ds.dims['lon'] / ds.dims['lat'], # for a sensible figsize
subplot_kws={'projection': map_proj}) # the plot's projection
# We have to set the map's options on all axes
for ax in p.axes.flat:
ax.coastlines()
ax.set_extent([-160, -30, 5, 75])
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-3-91c1107c19c0> in <module>
----> 1 air = ds.air.isel(time=[0, 724]) - 273.15
2
3 # This is the map projection we want to plot *onto*
4 map_proj = ccrs.LambertConformal(central_longitude=-95, central_latitude=45)
5
NameError: name 'ds' is not defined
Centered colormaps¶
Xarray’s automatic colormaps choice
[4]:
air = ds.air.isel(time=0)
f, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2, figsize=(8, 6))
# The first plot (in kelvins) chooses "viridis" and uses the data's min/max
air.plot(ax=ax1, cbar_kwargs={'label': 'K'})
ax1.set_title('Kelvins: default')
ax2.set_xlabel('')
# The second plot (in celsius) now chooses "BuRd" and centers min/max around 0
airc = air - 273.15
airc.plot(ax=ax2, cbar_kwargs={'label': '°C'})
ax2.set_title('Celsius: default')
ax2.set_xlabel('')
ax2.set_ylabel('')
# The center doesn't have to be 0
air.plot(ax=ax3, center=273.15, cbar_kwargs={'label': 'K'})
ax3.set_title('Kelvins: center=273.15')
# Or it can be ignored
airc.plot(ax=ax4, center=False, cbar_kwargs={'label': '°C'})
ax4.set_title('Celsius: center=False')
ax4.set_ylabel('')
# Make it nice
plt.tight_layout()
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-4-13691d1c0109> in <module>
----> 1 air = ds.air.isel(time=0)
2
3 f, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2, figsize=(8, 6))
4
5 # The first plot (in kelvins) chooses "viridis" and uses the data's min/max
NameError: name 'ds' is not defined
Control the plot’s colorbar¶
Use cbar_kwargs
keyword to specify the number of ticks. The spacing
kwarg can be used to draw proportional ticks.
[5]:
air2d = ds.air.isel(time=500)
# Prepare the figure
f, (ax1, ax2, ax3) = plt.subplots(1, 3, figsize=(14, 4))
# Irregular levels to illustrate the use of a proportional colorbar
levels = [245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 310, 340]
# Plot data
air2d.plot(ax=ax1, levels=levels)
air2d.plot(ax=ax2, levels=levels, cbar_kwargs={'ticks': levels})
air2d.plot(ax=ax3, levels=levels, cbar_kwargs={'ticks': levels,
'spacing': 'proportional'})
# Show plots
plt.tight_layout()
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-5-eefd6d2158f3> in <module>
----> 1 air2d = ds.air.isel(time=500)
2
3 # Prepare the figure
4 f, (ax1, ax2, ax3) = plt.subplots(1, 3, figsize=(14, 4))
5
NameError: name 'ds' is not defined
Multiple lines from a 2d DataArray¶
Use xarray.plot.line
on a 2d DataArray to plot selections as multiple lines.
See plotting.multiplelines
for more details.
[6]:
air = ds.air - 273.15 # to celsius
# Prepare the figure
f, (ax1, ax2) = plt.subplots(1, 2, figsize=(8, 4), sharey=True)
# Selected latitude indices
isel_lats = [10, 15, 20]
# Temperature vs longitude plot - illustrates the "hue" kwarg
air.isel(time=0, lat=isel_lats).plot.line(ax=ax1, hue='lat')
ax1.set_ylabel('°C')
# Temperature vs time plot - illustrates the "x" and "add_legend" kwargs
air.isel(lon=30, lat=isel_lats).plot.line(ax=ax2, x='time', add_legend=False)
ax2.set_ylabel('')
# Show
plt.tight_layout()
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-6-2c471b645252> in <module>
----> 1 air = ds.air - 273.15 # to celsius
2
3 # Prepare the figure
4 f, (ax1, ax2) = plt.subplots(1, 2, figsize=(8, 4), sharey=True)
5
NameError: name 'ds' is not defined
imshow()
and rasterio map projections¶
Using rasterio’s projection information for more accurate plots.
This example extends recipes.rasterio
and plots the image in the original map projection instead of relying on pcolormesh and a map transformation.
[7]:
url = 'https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif'
da = xr.open_rasterio(url)
# The data is in UTM projection. We have to set it manually until
# https://github.com/SciTools/cartopy/issues/813 is implemented
crs = ccrs.UTM('18N')
# Plot on a map
ax = plt.subplot(projection=crs)
da.plot.imshow(ax=ax, rgb='band', transform=crs)
ax.coastlines('10m', color='r')
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in _acquire_with_cache_info(self, needs_lock)
198 try:
--> 199 file = self._cache[self._key]
200 except KeyError:
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/lru_cache.py in __getitem__(self, key)
52 with self._lock:
---> 53 value = self._cache[key]
54 self._cache.move_to_end(key)
KeyError: [<function open at 0x7faf8c0e3280>, ('https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif',), 'r', ()]
During handling of the above exception, another exception occurred:
CPLE_HttpResponseError Traceback (most recent call last)
rasterio/_base.pyx in rasterio._base.DatasetBase.__init__()
rasterio/_shim.pyx in rasterio._shim.open_dataset()
rasterio/_err.pyx in rasterio._err.exc_wrap_pointer()
CPLE_HttpResponseError: CURL error: Could not resolve host: github.com
During handling of the above exception, another exception occurred:
RasterioIOError Traceback (most recent call last)
<ipython-input-7-de06099ce2ea> in <module>
1 url = 'https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif'
----> 2 da = xr.open_rasterio(url)
3
4 # The data is in UTM projection. We have to set it manually until
5 # https://github.com/SciTools/cartopy/issues/813 is implemented
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/rasterio_.py in open_rasterio(filename, parse_coordinates, chunks, cache, lock)
240
241 manager = CachingFileManager(rasterio.open, filename, lock=lock, mode="r")
--> 242 riods = manager.acquire()
243 if vrt_params is not None:
244 riods = WarpedVRT(riods, **vrt_params)
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in acquire(self, needs_lock)
179 An open file object, as returned by ``opener(*args, **kwargs)``.
180 """
--> 181 file, _ = self._acquire_with_cache_info(needs_lock)
182 return file
183
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in _acquire_with_cache_info(self, needs_lock)
203 kwargs = kwargs.copy()
204 kwargs["mode"] = self._mode
--> 205 file = self._opener(*self._args, **kwargs)
206 if self._mode == "w":
207 # ensure file doesn't get overriden when opened again
/usr/lib/python3/dist-packages/rasterio/env.py in wrapper(*args, **kwds)
431
432 with env_ctor(session=session):
--> 433 return f(*args, **kwds)
434
435 return wrapper
/usr/lib/python3/dist-packages/rasterio/__init__.py in open(fp, mode, driver, width, height, count, crs, transform, dtype, nodata, sharing, **kwargs)
219 # None.
220 if mode == 'r':
--> 221 s = DatasetReader(path, driver=driver, sharing=sharing, **kwargs)
222 elif mode == "r+":
223 s = get_writer_for_path(path, driver=driver)(
rasterio/_base.pyx in rasterio._base.DatasetBase.__init__()
RasterioIOError: CURL error: Could not resolve host: github.com
Parsing rasterio geocoordinates¶
Converting a projection’s cartesian coordinates into 2D longitudes and latitudes.
These new coordinates might be handy for plotting and indexing, but it should be kept in mind that a grid which is regular in projection coordinates will likely be irregular in lon/lat. It is often recommended to work in the data’s original map projection (see recipes.rasterio_rgb
).
[8]:
from rasterio.warp import transform
import numpy as np
url = 'https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif'
da = xr.open_rasterio(url)
# Compute the lon/lat coordinates with rasterio.warp.transform
ny, nx = len(da['y']), len(da['x'])
x, y = np.meshgrid(da['x'], da['y'])
# Rasterio works with 1D arrays
lon, lat = transform(da.crs, {'init': 'EPSG:4326'},
x.flatten(), y.flatten())
lon = np.asarray(lon).reshape((ny, nx))
lat = np.asarray(lat).reshape((ny, nx))
da.coords['lon'] = (('y', 'x'), lon)
da.coords['lat'] = (('y', 'x'), lat)
# Compute a greyscale out of the rgb image
greyscale = da.mean(dim='band')
# Plot on a map
ax = plt.subplot(projection=ccrs.PlateCarree())
greyscale.plot(ax=ax, x='lon', y='lat', transform=ccrs.PlateCarree(),
cmap='Greys_r', add_colorbar=False)
ax.coastlines('10m', color='r')
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in _acquire_with_cache_info(self, needs_lock)
198 try:
--> 199 file = self._cache[self._key]
200 except KeyError:
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/lru_cache.py in __getitem__(self, key)
52 with self._lock:
---> 53 value = self._cache[key]
54 self._cache.move_to_end(key)
KeyError: [<function open at 0x7faf8c0e3280>, ('https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif',), 'r', ()]
During handling of the above exception, another exception occurred:
CPLE_OpenFailedError Traceback (most recent call last)
rasterio/_base.pyx in rasterio._base.DatasetBase.__init__()
rasterio/_shim.pyx in rasterio._shim.open_dataset()
rasterio/_err.pyx in rasterio._err.exc_wrap_pointer()
CPLE_OpenFailedError: '/vsicurl/https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif' does not exist in the file system, and is not recognized as a supported dataset name.
During handling of the above exception, another exception occurred:
RasterioIOError Traceback (most recent call last)
<ipython-input-8-fec2e774fa84> in <module>
3
4 url = 'https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif'
----> 5 da = xr.open_rasterio(url)
6
7 # Compute the lon/lat coordinates with rasterio.warp.transform
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/rasterio_.py in open_rasterio(filename, parse_coordinates, chunks, cache, lock)
240
241 manager = CachingFileManager(rasterio.open, filename, lock=lock, mode="r")
--> 242 riods = manager.acquire()
243 if vrt_params is not None:
244 riods = WarpedVRT(riods, **vrt_params)
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in acquire(self, needs_lock)
179 An open file object, as returned by ``opener(*args, **kwargs)``.
180 """
--> 181 file, _ = self._acquire_with_cache_info(needs_lock)
182 return file
183
/build/python-xarray-6gtuKj/python-xarray-0.16.2/xarray/backends/file_manager.py in _acquire_with_cache_info(self, needs_lock)
203 kwargs = kwargs.copy()
204 kwargs["mode"] = self._mode
--> 205 file = self._opener(*self._args, **kwargs)
206 if self._mode == "w":
207 # ensure file doesn't get overriden when opened again
/usr/lib/python3/dist-packages/rasterio/env.py in wrapper(*args, **kwds)
431
432 with env_ctor(session=session):
--> 433 return f(*args, **kwds)
434
435 return wrapper
/usr/lib/python3/dist-packages/rasterio/__init__.py in open(fp, mode, driver, width, height, count, crs, transform, dtype, nodata, sharing, **kwargs)
219 # None.
220 if mode == 'r':
--> 221 s = DatasetReader(path, driver=driver, sharing=sharing, **kwargs)
222 elif mode == "r+":
223 s = get_writer_for_path(path, driver=driver)(
rasterio/_base.pyx in rasterio._base.DatasetBase.__init__()
RasterioIOError: '/vsicurl/https://github.com/mapbox/rasterio/raw/master/tests/data/RGB.byte.tif' does not exist in the file system, and is not recognized as a supported dataset name.