Creating an Ensemble of Fields

Creating an ensemble of random fields would also be a great idea. Let’s reuse most of the previous code.

We will set the position tuple pos before generation to reuse it afterwards.

import matplotlib.pyplot as pt
import numpy as np

import gstools as gs

x = y = np.arange(100)

model = gs.Gaussian(dim=2, var=1, len_scale=10)
srf = gs.SRF(model)
srf.set_pos([x, y], "structured")

This time, we did not provide a seed to SRF, as the seeds will used during the actual computation of the fields. We will create four ensemble members, for better visualisation, save them in to srf class and in a first step, we will be using the loop counter as the seeds.

ens_no = 4
for i in range(ens_no):
    srf(seed=i, store=f"field{i}")

Now let’s have a look at the results. We can access the fields by name or index:

fig, ax = pt.subplots(2, 2, sharex=True, sharey=True)
ax = ax.flatten()
for i in range(ens_no):
    ax[i].imshow(srf[i].T, origin="lower")
pt.show()

Using better Seeds

It is not always a good idea to use incrementing seeds. Therefore GSTools provides a seed generator MasterRNG. The loop, in which the fields are generated would then look like

from gstools.random import MasterRNG

seed = MasterRNG(20170519)
for i in range(ens_no):
    srf(seed=seed(), store=f"better_field{i}")