Some examples

These examples are meant to illustrate the relative simplicity of handling and use of the library, as well as a quick glance at its possibilities.

For a more comprehensive introduction to the package, please refer to the Tutorial.

For more advanced examples, please refer to the Gallery.

About Resources

• Open a resource and list its contents:

  >>> import epygram
  >>> epygram.init_env()
  >>> fcst5 = epygram.formats.resource(filename='../ICMSHAROM+0005', openmode='r')
  

  And, get the list of its fields:

  >>> fcst5.listfields()
  ['SPECSURFGEOPOTEN', 'SURFPRESSION', 'S001WIND.U.PHYS', 'S002WIND.U.PHYS', ...]
  

• Read a field in a resource:

  >>> surftemp = fcst5.readfield('SURFTEMPERATURE')
  >>> print surftemp
  H2DField containing:
      comment: __unknown__
      fid:
          FA: SURFTEMPERATURE
      geometry: H2DGeometry containing:
          projection:
             ...
      processtype: forecast
      spectral_geometry: __unknown__
      data: [[ 279.93986033   ...,  296.24581933]]
      validity: FieldValidity containing:
          ...
  

And many other features depending on the format…

---

FA: Some specific features

• Open a new FA sharing its geometry and validity with an existing one:

  >>> import epygram
  >>> epygram.init_env()
  >>> fcst5 = epygram.formats.resource(filename='../ICMSHAROM+0005', openmode='r', fmt='FA')
  >>> new_fcst5 = epygram.formats.resource(filename='../ICMSHAROM+0005_bis', openmode='w',
                                           fmt='FA',
                                           headername=fcst5.headername, validity=fcst5.validity)
  

• If you want it to be even more similar, also add arguments:

  >>> new_fcst5 = epygram.formats.resource(filename='../ICMSHAROM+0005_bis', openmode='w',
                                           fmt='FA',
                                           headername=fcst5.headername, validity=fcst5.validity,
                                           cdiden=fcst5.cdiden,
                                           default_compression=fcst5.default_compression,
                                           processtype=fcst5.processtype)
  

---

About Fields

• Read a spectral field, convert it to gridpoint, modify values, and get back to spectral space:

  >>> s30temp = fcst5.readfield('S030TEMPERATURE')
  >>> s30temp.spectral
  True
  >>> sp_geom = s30temp.spectral_geometry # save info about spectral geometry (lost after conversion)
  >>> s30temp.sp2gp() # conversion (in place) to gridpoint
  >>> s30temp.spectral
  False
  >>> s30temp.mean(subzone='CI')
  268.2468305845095
  >>> s30temp.spectral_geometry
  None
  >>> data = s30temp.data
  >>> data[10:-10,20:-20] = data[10:-10,20:-20] + 2 # heat the "center" by 2K
  >>> s30temp.setdata(data)
  >>> s30temp.mean(subzone='CI')
  270.14124437511464
  >>> s30temp.gp2sp(sp_geom)
  >>> s30temp.spectral
  True
  

• Compute the magnitude of wind rotation between two levels (it’s just an example…):

  >>> wfields = fcst5.readfields('S03[0-1]WIND.?.PHYS')
  >>> type(wfields)
  <class 'epygram.base.FieldSet'>
  >>> wfields.listfields('FA')
  ['S030WIND.U.PHYS', 'S031WIND.U.PHYS', 'S030WIND.V.PHYS', 'S031WIND.V.PHYS']
  >>> for f in wfields:
  ...     f.sp2gp()
  ...
  >>> du = wfields[0]-wfields[1]
  >>> dv = wfields[2]-wfields[3]
  >>> rot = du*du + dv*dv
  >>> rot.mean()
  1.3670194410302572
  >>> rot.plotfield() # rot is still a Field object
  

• Compute the windspeed:

  >>> import matplotlib.pyplot as plt
  >>> u = fcst5.readfield('S030WIND.U.PHYS')
  >>> v = fcst5.readfield('S030WIND.V.PHYS')
  >>> vectwind = epygram.fields.make_vector_field(u, v)
  >>> vectwind.sp2gp()
  >>> FF = vectwind.to_module()
  

---

About Geometry

• Get the lon/lat coordinates of the whole grid of a field, the corresponding max map factor, ask for the lower-right corner and checks whether a point is inside grid:

  >>> (lons, lats) = s30temp.geometry.get_lonlat_grid()
  (array([[ -8.3539362, ..., 12.6589942],
                        ...
          [-11.8154972, ..., 16.2188262]]),
   array([[ 37.3330505, ..., 37.3009714],
                        ...
          [ 53.2651904, ..., 53.2224197]]))
  >>> s30temp.geometry.map_factor_field().max()
  1.0108440620737038
  >>> s30temp.geometry.gimme_corners_ll()['lr']
  (12.658994623143194, 37.300971400173346)
  >>> s30temp.geometry.point_is_inside_domain(15.0, 37.0)
  False