Post processing

Tutorial

LADiM comes with a simple python package postladim that can be used for visualisation and analysis of LADiM output. It is based on the xarray package http://xarray.pydata.org/en/stable/.

Under reconstruction

class InstanceVariable

da

The underlying xarray DataArray

count

Number of particles at given time

time

The time steps

num_particles

The number of distinct particles

isel(time=n)

Select by time index, V.isel(time=n) = V[n]

sel(time=t, pid=p)

Select by time value and/or pid value

V.sel(time=‘2019-09-19 12’) selects particles at that time value V.sel(pid=23) selects the time history of particle with that pid value V.sel(time=‘2019-09-19 12’, pid=23) selects the unique particle instance

full()

Return the full 2D DataArray. May become vary large.

The InstanceVariable class support item notation:

V[n] = V.isel(time=n)
V[n, p] = V.isel(time=n).sel(pid=p)

len(V) == len(V.time) is the length of the time axis

Note that V[n, p] may be different from V[n][p] if particles have been removed.

class ParticleVariable

This class represents a variable that depends on the particle, but is independent of time.

da

Underlying xarray DataArray

Supports item notation:

V[p] is value of particle with pid = p

The basic class is postladim.ParticleFile, it is initiated by the following lines:

from postladim import ParticleFile
...
pf = ParticleFile('ladim-output.nc')

class ParticleFile(particle_file)

It has the following attributes:

ds

The underlying xarray Dataset.

num_times

Number of time frames in the file.

count

Numpy ndarray of particle counts at different time steps

start

ndarray of start indices at different time step

end

ndarray of end indices, short hand for pf.start + pf.count

instance_variables

List of particle instance variables

particle_variables

List of particle variables.

time

xarray DataArray of time stamps

position(n)

Tuple with position (X and Y) of particle-distribution at n-th time time. pf.position(n) = (pf[‘X’][n], pf[‘Y’][n])

trajectory(pid)

Returns a tuple of X and Y coordinates of the particle with identifier pid. trajectory(pid) = (pf[‘X’].sel(pid=pid), pf[‘Y’].sel(pid=pid))

variables

Deprecated, dictionary of variables, pf.variables[‘X’] = pf[‘X’] = pf.X

time(n)

Deprecated, pf.time(n) = pf.time[n].values

particle_count(n)

Deprecated, pf.particle_count(n) = pf.count[n]