Simple initial SOC feature

[larer]

There is a long example in your package about how to set the SOC. But I found a way to do do it much easier.
I added an input to the EISSimulation class in the constructor "init function" I added a line 49:
initial_soc=1.0,

Then in the build line 65 I added a feature to pass initial_soc to the build function.
sim.build(initial_soc=initial_soc)

This gives the same result as the more complex example, that is provided in the package.
I think the initial_soc feature in the build() is easy to use.

PS I am a beginner, learning both PyBAMM and Python so this suggestion might be a bad way to do it but it did the trick for me.

Now I am running the example using the following code

import matplotlib.pyplot as plt
import numpy as np
import pybamm

import pybammeis

# Load model
model = pybamm.lithium_ion.SPM(options={"surface form": "differential"})

# Set up parameters with cell SOC as an input parameter
parameter_values = pybamm.ParameterValues("Chen2020")

# Create simulation
# Choose frequencies and calculate impedance, looping over input parameter values
# and adding the results to a Nyquist plot
frequencies = np.logspace(-4, 4, 100)
_, ax = plt.subplots()
SOC_list=[0.01, 0.1, 0.5, 0.9, 0.99]
for z in SOC_list:
    eis_sim = pybammeis.EISSimulation(model, parameter_values=parameter_values, initial_soc=z)
    eis_sim.solve(frequencies)
    eis_sim.nyquist_plot(ax=ax, label=f"SOC = {z}")
ax.set_xlim([0, 0.08])
ax.set_ylim([0, 0.08])
ax.legend()
plt.show()

[rtimms]

Thanks! This would be a nice addition. I think for consistency with PyBaMM's Simulation class, initial_soc should be passed to solve, see https://github.com/pybamm-team/PyBaMM/blob/6c7c21aa1e2e8d4b51210b13ccca505566b1d910/src/pybamm/simulation.py#L395