analysis

analysis

Additional analysis functions that are not part of the core Covasim workflow, but which are useful for particular investigations: the analyzers (which run during a sim, e.g. cv.snapshot), cv.Fit and cv.Calibration (which compare a sim with data), and cv.TransTree (the transmission tree).

Classes

Name Description
Analyzer Base class for Covasim analyzers, built on ss.Analyzer.
Calibration A class to handle calibration of Covasim simulations. Uses the Optuna hyperparameter
Fit A class for calculating the fit between the model and the data. Note the
PeopleSnapshot A copy of the per-agent states of sim.people at one point in time (as stored by cv.snapshot).
TransTree A class for holding a transmission tree. There are several different representations
age_histogram Calculate statistics across age bins, including histogram plotting functionality.
daily_age_stats Calculate daily counts by age, saving for each day of the simulation. Can
daily_stats Print out daily statistics about the simulation. Note that this analyzer takes
nab_histogram Store histogram of log_{10}(NAb) distribution
snapshot Analyzer that takes a “snapshot” of the sim.people array at specified points

Analyzer

analysis.Analyzer(
    *args,
    do_plot=None,
    show_label=None,
    line_args=None,
    **kwargs,
)

Base class for Covasim analyzers, built on ss.Analyzer.

As in v3, an analyzer can define initialize(self, sim), apply(self, sim) (called on each timestep), and finalize(self, sim); or the Starsim equivalents init_post(), step(), and finalize().

Note: a custom analyzer must not store data under the names Starsim reserves on a module (t, pars, sim, dists, results) – use e.g. self.tvec instead of self.t.

Calibration

analysis.Calibration(
    sim,
    calib_pars=None,
    fit_args=None,
    custom_fn=None,
    par_samplers=None,
    n_trials=None,
    n_workers=None,
    total_trials=None,
    name=None,
    db_name=None,
    keep_db=None,
    storage=None,
    label=None,
    die=False,
    verbose=True,
    data=None,
    weights=None,
    fit_kw=None,
    reseed=False,
)

A class to handle calibration of Covasim simulations. Uses the Optuna hyperparameter optimization library (optuna.org), via Starsim’s ss.Calibration.

Each trial copies the sim, sets the trial’s parameter values (via sim[key] = value), runs it, and computes the fit to the data (sim.compute_fit()); Optuna then minimizes the mismatch.

Note: running a calibration does not guarantee a good fit! You must ensure that you run for a sufficient number of iterations, have enough free parameters, and that the parameters have wide enough bounds. Please see the tutorial on calibration for more information.

Parameters

Name Type Description Default
sim (Sim) the simulation to calibrate (ideally not yet initialized, so that parameters used during initialization, such as pop_infected, can be calibrated) required
calib_pars (dict) a dictionary of the parameters to calibrate of the format dict(key1=[best, low, high]) required
fit_args (dict) a dictionary of options that are passed to sim.compute_fit() to calculate the goodness-of-fit (e.g. data, weights, keys) required
custom_fn (func) a custom function for modifying the simulation; receives the sim and calib_pars as inputs, should return the modified sim. The sim has been initialized, so e.g. sim.get_intervention() can be used; calib_pars keys that are sim parameters have already been set. required
par_samplers (dict) an optional mapping from parameters to the Optuna sampler to use for choosing new points for each; by default, suggest_float required
n_trials (int) the number of trials per worker (default 20) required
n_workers (int) the number of parallel workers (default: the number of CPUs) required
total_trials (int) if supplied, the total number of trials, divided between the workers (overrides n_trials) required
name (str) the name of the Optuna study (default: ‘covasim_calibration’) required
db_name (str) the name of the database file (default: a file in a temporary folder, or f’{name}.db’ if name is supplied) required
keep_db (bool) whether to keep the database after calibration (default: false) required
storage (str) the location of the database (default: sqlite) required
label (str) a label for this calibration object required
die (bool) whether to stop if an exception is encountered (default: false) required
verbose (bool) whether to print details of the calibration required
data (df) shortcut for fit_args[‘data’]: the data to fit to (default: the sim’s data) required
weights (dict) shortcut for fit_args[‘weights’]: the weight of each result key required
fit_kw (dict) alias for fit_args required
reseed (bool) whether to use a different random seed for each trial (default: false) required

Example::

sim = cv.Sim(datafile='data.csv')
calib_pars = dict(beta=[0.015, 0.010, 0.020])
calib = cv.Calibration(sim, calib_pars, total_trials=100)
calib.calibrate()
calib.plot_sims()

Methods

Name Description
calibrate Actually perform calibration.
check_fit Check whether calibration improved the fit, by comparing the mismatch of the sims run before and
parse_study Parse the study into a data frame (self.df), in the order the trials were run – called automatically.
plot Alias to plot_sims()
plot_all Plot every point in the calibration. Warning, very slow for more than a few hundred trials.
plot_best Plot only the points with lowest mismatch.
plot_final Alias to plot_sims()
plot_sims Plot sims, before and after calibration.
plot_stride Plot a fixed number of points in order across the results.
plot_trend Plot the trend in best mismatch over time.
run_sim Create and run a simulation with the supplied parameter values, and compute its fit.
run_trial Define the objective for Optuna: sample the parameters, and return the mismatch
summarize Print out results from the calibration
calibrate
analysis.Calibration.calibrate(calib_pars=None, verbose=True, **kwargs)

Actually perform calibration.

Parameters
Name Type Description Default
calib_pars dict if supplied, overwrite stored calib_pars None
verbose bool whether to print a summary of the results True
kwargs dict if supplied, overwrite stored run_args (n_trials, n_workers, etc.) {}
check_fit
analysis.Calibration.check_fit(do_plot=True)

Check whether calibration improved the fit, by comparing the mismatch of the sims run before and after calibration (see also summarize()).

Parameters
Name Type Description Default
do_plot bool whether to plot the sims before and after calibration True
Returns
Name Type Description
True if the fit improved
parse_study
analysis.Calibration.parse_study(study=None)

Parse the study into a data frame (self.df), in the order the trials were run – called automatically.

Parameters
Name Type Description Default
study Study the Optuna study to parse (default: self.study) None
plot
analysis.Calibration.plot(**kwargs)

Alias to plot_sims()

plot_all
analysis.Calibration.plot_all()

Plot every point in the calibration. Warning, very slow for more than a few hundred trials.

plot_best
analysis.Calibration.plot_best(best_thresh=2)

Plot only the points with lowest mismatch.

Parameters
Name Type Description Default
best_thresh float plot the trials with a mismatch within this factor of the best mismatch 2
plot_final
analysis.Calibration.plot_final(**kwargs)

Alias to plot_sims()

plot_sims
analysis.Calibration.plot_sims(**kwargs)

Plot sims, before and after calibration.

Parameters
Name Type Description Default
kwargs dict passed to MultiSim.plot(), e.g. to_plot {}
plot_stride
analysis.Calibration.plot_stride(npts=200)

Plot a fixed number of points in order across the results.

Parameters
Name Type Description Default
npts int the number of points to plot 200
plot_trend
analysis.Calibration.plot_trend(best_thresh=2)

Plot the trend in best mismatch over time.

Parameters
Name Type Description Default
best_thresh float in the lower panel, show the trials with a mismatch within this factor of the best mismatch 2
run_sim
analysis.Calibration.run_sim(calib_pars, label=None, return_sim=False)

Create and run a simulation with the supplied parameter values, and compute its fit.

Parameters
Name Type Description Default
calib_pars dict the parameter values to use, e.g. dict(beta=0.015) required
label str if supplied, the label of the sim None
return_sim bool whether to return the sim (with its fit in sim.fit) rather than the mismatch False
Returns
Name Type Description
The mismatch (or the sim if return_sim=True); inf (or None) if the sim could not be run
run_trial
analysis.Calibration.run_trial(trial)

Define the objective for Optuna: sample the parameters, and return the mismatch

summarize
analysis.Calibration.summarize()

Print out results from the calibration

Fit

analysis.Fit(
    sim,
    weights=None,
    keys=None,
    custom=None,
    compute=True,
    verbose=False,
    die=True,
    label=None,
    data=None,
    **kwargs,
)

A class for calculating the fit between the model and the data. Note the following terminology is used here:

- fit: nonspecific term for how well the model matches the data
- difference: the absolute numerical differences between the model and the data (one time series per result)
- goodness-of-fit: the result of passing the difference through a statistical function, such as mean squared error
- loss: the goodness-of-fit for each result multiplied by user-specified weights (one time series per result)
- mismatches: the sum of all the losses (a single scalar value per time series)
- mismatch: the sum of the mismatches -- this is the value to be minimized during calibration

Parameters

Name Type Description Default
sim Sim the sim object (after it has been run) required
weights dict the relative weight to place on each result (by default: 10 for deaths, 5 for diagnoses, 1 for everything else) None
keys list the keys to use in the calculation None
custom dict a custom dictionary of additional data to fit; format is e.g. {‘my_output’:{‘data’:[1,2,3], ‘sim’:[1,2,4], ‘weights’:2.0}} None
compute bool whether to compute the mismatch immediately True
verbose bool detail to print False
die bool whether to raise an exception if no data are supplied True
label str the label for the fit None
data DataFrame the data to fit, indexed by date or by integer day, with columns named like the sim results (e.g. cum_deaths); by default, the sim’s data (sim.data) None
kwargs dict passed to cv.compute_gof() – see this function for more detail on goodness-of-fit calculation options {}

Example::

sim = cv.Sim(datafile='my-data-file.csv')
sim.run()
fit = sim.compute_fit()
fit.plot()

Methods

Name Description
compute Perform all required computations
compute_diffs Find the differences between the sim and the data
compute_gofs Compute the goodness-of-fit
compute_losses Compute the weighted goodness-of-fit
compute_mismatch Compute the final mismatch
plot Plot the fit of the model to the data. For each result, plot the data
reconcile_inputs Find matching keys and indices between the model and the data
summarize Print out results from the fit
compute
analysis.Fit.compute()

Perform all required computations

compute_diffs
analysis.Fit.compute_diffs(absolute=False)

Find the differences between the sim and the data

compute_gofs
analysis.Fit.compute_gofs(**kwargs)

Compute the goodness-of-fit

compute_losses
analysis.Fit.compute_losses()

Compute the weighted goodness-of-fit

compute_mismatch
analysis.Fit.compute_mismatch(use_median=False)

Compute the final mismatch

plot
analysis.Fit.plot(
    keys=None,
    width=0.8,
    fig_args=None,
    axis_args=None,
    plot_args=None,
    date_args=None,
    do_show=None,
    fig=None,
    **kwargs,
)

Plot the fit of the model to the data. For each result, plot the data and the model; the difference; and the loss (weighted difference). Also plots the loss as a function of time.

Parameters
Name Type Description Default
keys list which keys to plot (default, all) None
width float bar width 0.8
fig_args dict passed to plt.figure() None
axis_args dict passed to plt.subplots_adjust() None
plot_args dict passed to plt.plot() None
date_args dict passed to cv.plotting.reset_ticks() (handle date format, rotation, etc.) None
do_show bool whether to show the plot None
fig fig if supplied, use this figure to plot in None
kwargs dict passed to cv.options.with_style() {}
Returns
Name Type Description
Figure object
reconcile_inputs
analysis.Fit.reconcile_inputs()

Find matching keys and indices between the model and the data

summarize
analysis.Fit.summarize()

Print out results from the fit

PeopleSnapshot

analysis.PeopleSnapshot(sim, copy=True)

A copy of the per-agent states of sim.people at one point in time (as stored by cv.snapshot).

Every array is full length and indexed by agent (UID): agents who have died keep their last values (with dead=True and alive=False), so snapshots from different days can be compared elementwise. States are available as attributes or keys, e.g. people.exposed or people['age'], including the v3 names date_exposed, date_symptomatic, etc. (the ti_* time indices, since the timestep is one day).

Parameters

Name Type Description Default
sim Sim the sim to take the snapshot from required
copy bool whether to copy the arrays (default); if False, the stored states are not copied, so only use the snapshot on the current timestep True

Methods

Name Description
count The number of people for whom this state is true
defined The indices of people for whom this state is not NaN
false The indices of people for whom this state is false
keys The names of the stored states
true The indices of people for whom this state is true
undefined The indices of people for whom this state is NaN
count
analysis.PeopleSnapshot.count(key)

The number of people for whom this state is true

defined
analysis.PeopleSnapshot.defined(key)

The indices of people for whom this state is not NaN

false
analysis.PeopleSnapshot.false(key)

The indices of people for whom this state is false

keys
analysis.PeopleSnapshot.keys()

The names of the stored states

true
analysis.PeopleSnapshot.true(key)

The indices of people for whom this state is true

undefined
analysis.PeopleSnapshot.undefined(key)

The indices of people for whom this state is NaN

TransTree

analysis.TransTree(sim=None, to_networkx=False, **kwargs)

A class for holding a transmission tree. There are several different representations of the transmission tree: “infection_log” is copied from the sim and is the simplest representation. “detailed” includes additional attributes about the source and target. If NetworkX is installed (required for most methods), “graph” includes an NX representation of the transmission tree.

The transmission log is always recorded by the COVID module (sim.diseases.covid.infection_log), so the tree can be made from any sim after it has run. It can also be added as an analyzer (analyzers=cv.TransTree()), in which case it is made when the sim finishes.

Parameters

Name Type Description Default
sim Sim the sim object (if None, make the tree at the end of the run the analyzer is part of) None
to_networkx bool whether to convert the graph to a NetworkX object False

Example::

sim = cv.Sim()
sim.run()
tt = sim.make_transtree()
tt.plot()
tt.plot_histograms()

New in version 2.1.0: tt.detailed is a dataframe rather than a list of dictionaries; for the latter, use tt.detailed.to_dict('records').

Methods

Name Description
animate Animate the transmission tree.
count_targets Count the number of targets each infected person has. If start and/or end
count_transmissions Iterable over edges corresponding to transmission events
day Convenience function for converting an input to an integer day
get_people_attr Get a per-agent array from the people; the date someone became a known contact is not recorded, so that is all NaN
make_detailed Construct a detailed transmission tree, with additional information for each person (people is a cv.PeopleSnapshot)
make_tree Make the transmission tree from a sim that has been run
plot Plot the transmission tree.
plot_histograms Plots a histogram of the number of transmissions.
r0 Return average number of transmissions per person
animate
analysis.TransTree.animate(*args, **kwargs)

Animate the transmission tree.

Parameters
Name Type Description Default
animate bool whether to animate the plot (otherwise, show when finished) required
verbose bool print out progress of each frame required
markersize int size of the markers required
sus_color list color for susceptibles required
fig_args dict arguments passed to plt.figure() required
axis_args dict arguments passed to plt.subplots_adjust() required
plot_args dict arguments passed to plt.plot() required
delay float delay between frames in seconds required
colors list color of each person required
cmap str colormap for each person (if colors is not supplied) required
fig fig if supplied, use this figure required
Returns
Name Type Description
fig the figure object
count_targets
analysis.TransTree.count_targets(start_day=None, end_day=None)

Count the number of targets each infected person has. If start and/or end days are given, it will only count the targets of people who got infected between those dates (it does not, however, filter on the date the target got infected).

Parameters
Name Type Description Default
start_day int / str the day on which to start counting people who got infected None
end_day int / str the day on which to stop counting people who got infected None
count_transmissions
analysis.TransTree.count_transmissions()

Iterable over edges corresponding to transmission events

This excludes edges corresponding to seeded infections without a source

day
analysis.TransTree.day(day=None, which=None)

Convenience function for converting an input to an integer day

get_people_attr
analysis.TransTree.get_people_attr(people, attr)

Get a per-agent array from the people; the date someone became a known contact is not recorded, so that is all NaN

make_detailed
analysis.TransTree.make_detailed(people)

Construct a detailed transmission tree, with additional information for each person (people is a cv.PeopleSnapshot)

make_tree
analysis.TransTree.make_tree(sim)

Make the transmission tree from a sim that has been run

plot
analysis.TransTree.plot(fig_args=None, plot_args=None, do_show=None, fig=None)

Plot the transmission tree.

Parameters
Name Type Description Default
fig_args dict passed to plt.figure() None
plot_args dict passed to plt.plot() None
do_show bool whether to show the plot None
fig fig if supplied, use this figure None
plot_histograms
analysis.TransTree.plot_histograms(
    start_day=None,
    end_day=None,
    bins=None,
    width=0.8,
    fig_args=None,
    fig=None,
)

Plots a histogram of the number of transmissions.

Parameters
Name Type Description Default
start_day int / str the day on which to start counting people who got infected None
end_day int / str the day on which to stop counting people who got infected None
bins list bin edges to use for the histogram None
width float width of bars 0.8
fig_args dict passed to plt.figure() None
fig fig if supplied, use this figure None
r0
analysis.TransTree.r0(recovered_only=False)

Return average number of transmissions per person

This doesn’t include seed transmissions. By default, it also doesn’t adjust for length of infection (e.g. people infected towards the end of the simulation will have fewer transmissions because their infection may extend past the end of the simulation, these people are not included). If ‘recovered_only=True’ then the downstream transmissions will only be included for people that recover before the end of the simulation, thus ensuring they all had the same amount of time to transmit.

age_histogram

analysis.age_histogram(
    days=None,
    states=None,
    edges=None,
    datafile=None,
    sim=None,
    die=True,
    **kwargs,
)

Calculate statistics across age bins, including histogram plotting functionality.

For each state, the histogram counts the people for whom that state’s date is defined (e.g. date_exposed), i.e. the cumulative number of people who have been (or are scheduled to be) in that state.

Parameters

Name Type Description Default
days list list of ints/strings/date objects, the days on which to calculate the histograms (default: last day) None
states list which states of people to record (default: exposed, severe, dead, tested, diagnosed) None
edges list edges of age bins to use (default: 10 year bins from 0 to 100) None
datafile str the name of the data file to load in for comparison, or a dataframe of data (optional) None
sim Sim only used if the analyzer is being used after a sim has already been run None
die bool whether to raise an exception if dates are not found (default true) True
kwargs dict passed to Analyzer() {}

Examples::

sim = cv.Sim(analyzers=cv.age_histogram())
sim.run()

agehist = sim.get_analyzer()
agehist = cv.age_histogram(sim=sim) # Alternate method
agehist.plot()

Methods

Name Description
compute_windows Convert cumulative histograms to windows
from_sim Create an age histogram from an already run sim
get Retrieve a specific histogram from the given key (int, str, or date)
plot Simple method for plotting the histograms.
compute_windows
analysis.age_histogram.compute_windows()

Convert cumulative histograms to windows

from_sim
analysis.age_histogram.from_sim(sim)

Create an age histogram from an already run sim

get
analysis.age_histogram.get(key=None)

Retrieve a specific histogram from the given key (int, str, or date)

plot
analysis.age_histogram.plot(
    windows=False,
    width=0.8,
    color='#F8A493',
    fig_args=None,
    axis_args=None,
    data_args=None,
    **kwargs,
)

Simple method for plotting the histograms.

Parameters
Name Type Description Default
windows bool whether to plot windows instead of cumulative counts False
width float width of bars 0.8
color hex or rgb the color of the bars '#F8A493'
fig_args dict passed to pl.figure() None
axis_args dict passed to pl.subplots_adjust() None
data_args dict ‘width’, ‘color’, and ‘offset’ arguments for the data None
kwargs dict passed to cv.options.with_style(); see that function for choices {}
Returns
Name Type Description
A list of figures, one per day

daily_age_stats

analysis.daily_age_stats(states=None, edges=None, **kwargs)

Calculate daily counts by age, saving for each day of the simulation. Can plot either time series by age or a histogram over all time.

The counts are stored in age_results (v3: results, which is reserved by Starsim for time-series results): age_results[date][state] is the number of people in each age bin whose date_{state} is that day.

Parameters

Name Type Description Default
states list which states of people to record (default: exposed, severe, dead, tested, diagnosed) None
edges list edges of age bins to use (default: 10 year bins from 0 to 100) None
kwargs dict passed to Analyzer() {}

Examples::

sim = cv.Sim(analyzers=cv.daily_age_stats())
sim.run()
daily_age = sim.get_analyzer()
daily_age.plot()
daily_age.plot(total=True)

Methods

Name Description
plot Plot the results.
to_df Create dataframe totals for each day
to_total_df Create dataframe totals across days
plot
analysis.daily_age_stats.plot(
    total=False,
    do_show=None,
    fig_args=None,
    axis_args=None,
    plot_args=None,
    dateformat=None,
    width=0.8,
    color='#F8A493',
    **kwargs,
)

Plot the results.

Parameters
Name Type Description Default
total bool whether to plot the total histograms rather than time series False
do_show bool whether to show the plot None
fig_args dict passed to pl.figure() None
axis_args dict passed to pl.subplots_adjust() None
plot_args dict passed to pl.plot() None
dateformat str the format to use for the x-axes (only used for time series) None
width float width of bars (only used for histograms) 0.8
color hex / rgb the color of the bars (only used for histograms) '#F8A493'
kwargs dict passed to cv.options.with_style() {}
to_df
analysis.daily_age_stats.to_df()

Create dataframe totals for each day

to_total_df
analysis.daily_age_stats.to_total_df()

Create dataframe totals across days

daily_stats

analysis.daily_stats(
    days=None,
    verbose=True,
    reporter=None,
    save_inds=False,
    **kwargs,
)

Print out daily statistics about the simulation. Note that this analyzer takes a considerable amount of time, so should be used primarily for debugging, not in production code. To keep the intervention but toggle it off, pass an empty list of days.

To show the stats for a day after a run has finished, use e.g. daily_stats.report('2020-04-04').

Parameters

Name Type Description Default
days list days on which to print out statistics (if None, assume all) None
verbose bool whether to print on each timestep True
reporter func if supplied, a custom parser of the stats object into a report (see make_report() function for syntax) None
save_inds bool whether to save the indices of every infection at every timestep (also recoverable from the infection log) False

Example::

sim = cv.Sim(analyzers=cv.daily_stats())
sim.run()
sim.get_analyzer().plot()

Methods

Name Description
intersect Compute the intersection between arrays of indices, handling either keys
make_report Turn the statistics into a report
plot Plot the daily statistics recorded. Some overlap with e.g. sim.plot(to_plot='overview').
report Print out one or all reports – take a date string, or an int for the position in the list of reports (not a day of the sim)
transpose Transpose the data from a list-of-dicts-of-dicts to a dict-of-dicts-of-lists
intersect
analysis.daily_stats.intersect(*args)

Compute the intersection between arrays of indices, handling either keys to precomputed indices or lists of indices. With two array inputs, simply performs np.intersect1d(arr1, arr2).

make_report
analysis.daily_stats.make_report(sim, stats, show_empty='count')

Turn the statistics into a report

plot
analysis.daily_stats.plot(
    fig_args=None,
    axis_args=None,
    plot_args=None,
    do_show=None,
    **kwargs,
)

Plot the daily statistics recorded. Some overlap with e.g. sim.plot(to_plot='overview').

Parameters
Name Type Description Default
fig_args dict passed to pl.figure() None
axis_args dict passed to pl.subplots_adjust() None
plot_args dict passed to pl.plot() None
do_show bool whether to show the plot None
kwargs dict passed to cv.options.with_style() {}
report
analysis.daily_stats.report(day=None)

Print out one or all reports – take a date string, or an int for the position in the list of reports (not a day of the sim)

transpose
analysis.daily_stats.transpose(keys=None)

Transpose the data from a list-of-dicts-of-dicts to a dict-of-dicts-of-lists

nab_histogram

analysis.nab_histogram(days=None, edges=None, **kwargs)

Store histogram of log_{10}(NAb) distribution

Parameters

Name Type Description Default
days list days on which calculate the NAb histogram (if None, assume last day) None
edges list log10 bin edges for histogram None

Example::

sim = cv.Sim(analyzers=cv.nab_histogram())
sim.run()
sim.get_analyzer().plot()

New in version 3.1.0.

Methods

Name Description
plot Plot the results
plot
analysis.nab_histogram.plot(
    fig_args=None,
    axis_args=None,
    plot_args=None,
    do_show=None,
    **kwargs,
)

Plot the results

Parameters
Name Type Description Default
fig_args dict passed to pl.figure() None
axis_args dict passed to pl.subplots_adjust() None
plot_args dict passed to pl.plot() None
do_show bool whether to show the plot None
kwargs dict passed to cv.options.with_style() {}

snapshot

analysis.snapshot(days, *args, die=True, **kwargs)

Analyzer that takes a “snapshot” of the sim.people array at specified points in time, and saves them to itself. To retrieve them, you can either access the dictionary directly, or use the get() method.

Each snapshot is a cv.PeopleSnapshot: full-length per-agent arrays, indexed by agent, with the same names as in v3 (e.g. people.exposed, people.age, people.date_symptomatic).

Parameters

Name Type Description Default
days list list of ints/strings/date objects, the days on which to take the snapshot required
args list additional day(s) ()
die bool whether or not to raise an exception if a date is not found (default true) True
kwargs dict passed to Analyzer() {}

Example::

sim = cv.Sim(analyzers=cv.snapshot('2020-04-04', '2020-04-14'))
sim.run()
snapshot = sim.get_analyzer()
people = snapshot.snapshots[0]            # Option 1
people = snapshot.snapshots['2020-04-04'] # Option 2
people = snapshot.get('2020-04-14')       # Option 3
people = snapshot.get(34)                 # Option 4
people = snapshot.get()                   # Option 5

Methods

Name Description
get Retrieve a snapshot from the given key (int, str, or date)
get
analysis.snapshot.get(key=None)

Retrieve a snapshot from the given key (int, str, or date)