`generate_arcs` function

[rogerkuou]

Create a function to generate arcs of a network from an STM.

import xarray as xr
from pydepsi.network import generate_arcs

stm_points = xr.open_zarr(`exmaple_stm.zarr`)

stm_arcs = generate_arcs(stm_points, method='delaunay')

def generate_arcs(stm_points, method='delaunay', min_length=50, max_length=1000, x='lon', y='lat'):
  pass

args:

• stm_points: input Space-Time Matrix in form of Xarray.Dataset.
• method: ways to form the network"delaunay" or "redundant"
• min_length/max_length: min/max length of the generated arc
• x/y: horizontal coordinates used to calculate the arcs

return

• stm_arcs: An STM in form of Xarray.Dataset, with each element in space an arc. Three data variables:
  • start_idx (space): index of starting point in stm_points
  • end_idx (space): index of end point in stm_points
  • diff_phase (sapce): phase diffencese end['phase'] - start['phase']

For delauney implementation, consider this one from scipy

Freek will provide the current implementation of redundant in MATLAB:

• https://bitbucket.org/grsradartudelft/depsi/src/master/main/ps_form_network.m
• https://bitbucket.org/grsradartudelft/depsi/src/master/main/ps_construct_redundant_network.m

Example notebook of retrieving and sparsing a STM: network.zip

[FreekvanLeijen]

@vanlankveldthijs You can find descriptions of the existing Matlab implementations in my thesis, see

https://resolver.tudelft.nl/uuid:5dba48d7-ee26-4449-b674-caa8df93e71e

Networks: page 50. Overall processing flow, see page 31.

[FreekvanLeijen]

@vanlankveldthijs As discussed, I realized that the Delaunay triangulation is also used in another function, where it is used to create a set of short, independent arcs between points. (Max 1 arc per point, not all points need to be used necessarily.)

See https://bitbucket.org/grsradartudelft/depsi/src/master/main/ps_vce.m

It would be nice if the (scipy) Delaunay function we are going to use, enables the same functionality (that is, provides the indices etc needed. But I guess it will.)

[vanlankveldthijs]

We decided not to add any attributes to the arcs. These can be collected from the points referenced.