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Using time unit

When using the SUND toolbox, the models, activities and simulations can all be defined in different time units, and still work together. In the example below, the model is defined in hours, the activity in minutes, and the simulation in seconds:

In the model

########## NAME
example_model
########## METADATA
time_unit = 'h'

In the activity

activity = sund.Activity(time_unit='m')

In the simulation

model = sund.load_model('example-model')

sim = sund.Simulation(time_unit = 's', models = [model], activities = [activity])

When the simulation is run, the values of the simulation will be in the time unit specified when creating the simulation.

Comparison of the time unit functionality

To illustrate this, you find a comparisons between simulations with the same model, different activity time units, and different model time units. As you can see, the simulation results are the same regardless of the time units.

tu_showcase

This image was generated from the code available below and this model file

# %% load packages
import os

import matplotlib.pyplot as plt
import numpy

import sund

# %% Install and load model
MODEL_NAME = 'tu_showcase'  # Example model name
sund.install_model(f"extras/{MODEL_NAME}.txt")  # Install the model if not already installed
model = sund.load_model(MODEL_NAME) 

# %% Define an activity and set its time_unit
activity_min = sund.Activity(time_unit='m')  # Set the time_unit for the activity
activity_min.add_output(sund.PIECEWISE_CONSTANT, "input", t = [0, 15], f=[0, 2, 0])

activity_hour = sund.Activity(time_unit='h')  # Set the time_unit for the activity
activity_hour.add_output(sund.PIECEWISE_CONSTANT, "input", t = [0, 0.25], f=[0, 2, 0])

# %% Create some simulation objects and set its time_unit
sim_min  = sund.Simulation(models=model, time_unit='m', activities=activity_min)  # Set the time_unit for the simulation
sim_hour = sund.Simulation(models=model, time_unit='h', activities=activity_min)  # Set the time_unit for the simulation

sim2_min = sund.Simulation(models=model,  time_unit='m', activities=activity_hour)  # Set the time_unit for the simulation
sim2_hour = sund.Simulation(models=model, time_unit='h', activities=activity_hour)  # Set the time_unit for the simulation

# %% Demonstrate how time_units interact
t_end_hour = 5
t_end_min  = 300 
sim_min.simulate(time_vector  = numpy.linspace(0, t_end_min, 300))   # Simulate 5h with the simulation in minutes
sim_hour.simulate(time_vector = numpy.linspace(0, t_end_hour, 300))  # Simulate 5h with the simulation in hours

sim2_min.simulate(time_vector  = numpy.linspace(0, t_end_min, 300))   # Simulate 5h with the simulation in minutes
sim2_hour.simulate(time_vector = numpy.linspace(0, t_end_hour, 300))  # Simulate 5h with the simulation in hours

# %% Plot the results
idx = model.feature_names.index('yA')

plt.figure('Figure 1', figsize=(8, 8))

ax1 = plt.subplot(1, 2, 1)
ax1.plot(sim_min.time_vector, sim_min.feature_data[:,idx], lw=2, label='Simulation in minutes')
ax1.plot(sim_hour.time_vector*60, sim_hour.feature_data[:,idx], lw=2, label='Simulation in hours', ls='dashed') # translate hours to minutes for the x-axis to match
ax1.set_xlabel('Time (min)')
ax1.set_ylabel('yA')
ax1.legend()
ax1.set_title('Activity with minute time_unit')

ax2 = plt.subplot(1, 2, 2)
ax2.plot(sim2_min.time_vector, sim2_min.feature_data[:,idx], lw=2, label='Simulation in minutes')
ax2.plot(sim2_hour.time_vector*60, sim2_hour.feature_data[:,idx], lw=2, label='Simulation in hours', ls='dashed') # translate hours to minutes for the x-axis to match
ax2.set_xlabel('Time (min)')
ax2.set_ylabel('yA')
ax2.legend()
ax2.set_title('Activity with hour time_unit')

os.makedirs('extras', exist_ok=True)  # Create the extras directory if it doesn't exist
plt.savefig('extras/time_units.png', dpi=300) # Save the figure as a PNG file in the extras directory

plt.show()