epiworldR

CRAN status R-CMD-check CRANlogs downloads License: MIT codecov

This R package is a wrapper of the C++ library epiworld. It provides a general framework for modeling disease transmission using agent-based models. Some of the main features include:

From the package’s description:

A flexible framework for Agent-Based Models (ABM), the epiworldR package provides methods for prototyping disease outbreaks and transmission models using a C++ backend, making it very fast. It supports multiple epidemiological models, including the Susceptible-Infected-Susceptible (SIS), Susceptible-Infected-Removed (SIR), Susceptible-Exposed-Infected-Removed (SEIR), and others, involving arbitrary mitigation policies and multiple-disease models. Users can specify infectiousness/susceptibility rates as a function of agents’ features, providing great complexity for the model dynamics. Furthermore, epiworldR is ideal for simulation studies featuring large populations.

Current available models:

  1. ModelDiffNet
  2. ModelSEIR
  3. ModelSEIRCONN
  4. ModelSEIRD
  5. ModelSEIRDCONN
  6. ModelSEIRMixing
  7. ModelSIR
  8. ModelSIRCONN
  9. ModelSIRD
  10. ModelSIRDCONN
  11. ModelSIRLogit
  12. ModelSIRMixing
  13. ModelSIS
  14. ModelSISD
  15. ModelSURV

Installation

You can install the development version of epiworldR from GitHub with:

devtools::install_github("UofUEpiBio/epiworldR")

Or from CRAN

install.packages("epiworldR")

Examples

This R package includes several popular epidemiological models, including SIS, SIR, and SEIR using either a fully connected graph (similar to a compartmental model) or a user-defined network.

SIR model using a random graph

This Susceptible-Infected-Recovered model features a population of 100,000 agents simulated in a small-world network. Each agent is connected to ten other agents. One percent of the population has the virus, with a 70% chance of transmission. Infected individuals recover at a 0.3 rate:

library(epiworldR)

# Creating a SIR model
sir <- ModelSIR(
  name              = "COVID-19",
  prevalence        = .01,
  transmission_rate = .7,
  recovery          = .3
) |>
  # Adding a Small world population
  agents_smallworld(n = 100000, k = 10, d = FALSE, p = .01) |>
  # Running the model for 50 days
  run(ndays = 50, seed = 1912)
#> _________________________________________________________________________
#> |Running the model...
#> |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| done.
#> | done.

sir
#> ________________________________________________________________________________
#> Susceptible-Infected-Recovered (SIR)
#> It features 100000 agents, 1 virus(es), and 0 tool(s).
#> The model has 3 states.
#> The final distribution is: 822 Susceptible, 415 Infected, and 98763 Recovered.

Visualizing the outputs

summary(sir)
#> ________________________________________________________________________________
#> ________________________________________________________________________________
#> SIMULATION STUDY
#>
#> Name of the model   : Susceptible-Infected-Recovered (SIR)
#> Population size     : 100000
#> Agents' data        : (none)
#> Number of entities  : 0
#> Days (duration)     : 50 (of 50)
#> Number of viruses   : 1
#> Last run elapsed t  : 62.00ms
#> Last run speed      : 79.47 million agents x day / second
#> Rewiring            : off
#>
#> Global events:
#>  (none)
#>
#> Virus(es):
#>  - COVID-19
#>
#> Tool(s):
#>  (none)
#>
#> Model parameters:
#>  - Recovery rate     : 0.3000
#>  - Transmission rate : 0.7000
#>
#> Distribution of the population at time 50:
#>   - (0) Susceptible :  99000 -> 822
#>   - (1) Infected    :   1000 -> 415
#>   - (2) Recovered   :      0 -> 98763
#>
#> Transition Probabilities:
#>  - Susceptible  0.91  0.09  0.00
#>  - Infected     0.00  0.70  0.30
#>  - Recovered    0.00  0.00  1.00
plot(sir)

plot_incidence(sir)

SEIR model with a fully connected graph

The SEIR model is similar to the SIR model but includes an exposed state. Here, we simulate a population of 10,000 agents with a 0.01 prevalence, a 0.6 transmission rate, a 0.5 recovery rate, and 7 days-incubation period. The population is fully connected, meaning agents can transmit the disease to any other agent:

model_seirconn <- ModelSEIRCONN(
  name                = "COVID-19",
  prevalence          = 0.01,
  n                   = 10000,
  contact_rate        = 10,
  incubation_days     = 7,
  transmission_rate   = 0.1,
  recovery_rate       = 1 / 7
) |> add_virus(
  virus(
    name = "COVID-19",
    prevalence = 0.01,
    as_proportion = TRUE,
    prob_infecting = 0.01,
    recovery_rate = 0.6,
    prob_death = 0.5,
    incubation = 7
))

set.seed(132)
run(model_seirconn, ndays = 100)
#> _________________________________________________________________________
#> Running the model...
#> ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| done.
#>  done.
summary(model_seirconn)
#> ________________________________________________________________________________
#> ________________________________________________________________________________
#> SIMULATION STUDY
#>
#> Name of the model   : Susceptible-Exposed-Infected-Removed (SEIR) (connected)
#> Population size     : 10000
#> Agents' data        : (none)
#> Number of entities  : 0
#> Days (duration)     : 100 (of 100)
#> Number of viruses   : 2
#> Last run elapsed t  : 15.00ms
#> Last run speed      : 64.01 million agents x day / second
#> Rewiring            : off
#>
#> Global events:
#>  - Update infected individuals (runs daily)
#>
#> Virus(es):
#>  - COVID-19
#>  - COVID-19
#>
#> Tool(s):
#>  (none)
#>
#> Model parameters:
#>  - Avg. Incubation days : 7.0000
#>  - Contact rate         : 10.0000
#>  - Prob. Recovery       : 0.1429
#>  - Prob. Transmission   : 0.1000
#>
#> Distribution of the population at time 100:
#>   - (0) Susceptible :  9800 -> 11
#>   - (1) Exposed     :   200 -> 0
#>   - (2) Infected    :     0 -> 3
#>   - (3) Recovered   :     0 -> 9986
#>
#> Transition Probabilities:
#>  - Susceptible  0.94  0.06  0.00  0.00
#>  - Exposed      0.00  0.85  0.15  0.00
#>  - Infected     0.00  0.00  0.86  0.14
#>  - Recovered    0.00  0.00  0.00  1.00

Computing some key statistics

plot(model_seirconn)


repnum <- get_reproductive_number(model_seirconn)

head(plot(repnum))

#>   virus_id    virus date      avg  n       sd    lb     ub
#> 1        0 COVID-19    0 5.769231 91 5.455022 1.000 20.750
#> 2        0 COVID-19    2 6.400000 10 4.880801 0.450 14.875
#> 3        0 COVID-19    3 5.166667 18 4.422536 0.425 13.000
#> 4        0 COVID-19    4 4.659091 44 3.784566 0.000 12.850
#> 5        0 COVID-19    5 5.205882 34 3.273210 0.000 12.175
#> 6        0 COVID-19    6 3.137255 51 2.713077 0.000  8.750

head(plot_generation_time(model_seirconn))

#>   date      avg  n       sd ci_lower ci_upper    virus virus_id
#> 1    2 4.444444  9 2.185813      2.2    8.000 COVID-19        0
#> 2    3 7.411765 17 3.922034      2.4   15.000 COVID-19        0
#> 3    4 8.538462 39 7.100208      2.0   22.000 COVID-19        0
#> 4    5 6.312500 32 3.905641      2.0   13.225 COVID-19        0
#> 5    6 7.200000 40 4.052223      2.0   15.100 COVID-19        0
#> 6    7 7.660000 50 4.461216      2.0   17.000 COVID-19        0

SIR Logit

This model provides a more complex transmission and recovery pattern based on agents’ features. With it, we can reflect co-morbidities that could change the probability of infection and recovery. Here, we simulate a population including a dataset with two features: an intercept and a binary variable Female. The probability of infection and recovery are functions of the intercept and the Female variables. The following code simulates a population of 100,000 agents in a small-world network. Each agent is connected to eight other agents. One percent of the population has the virus, with an 80% chance of transmission. Infected individuals recover at a 0.3 rate:

# Simulating a population of 100,000 agents
set.seed(2223)
n <- 100000

# Agents' features
X <- cbind(
  Intercept = 1,
  Female    = sample.int(2, n, replace = TRUE) - 1
)

coef_infect  <- c(.1, -2, 2)
coef_recover <- rnorm(2)

# Creating the model
model_logit <- ModelSIRLogit(
  "covid2",
  data = X,
  coefs_infect      = coef_infect,
  coefs_recover     = coef_recover,
  coef_infect_cols  = 1L:ncol(X),
  coef_recover_cols = 1L:ncol(X),
  prob_infection = .8,
  recovery_rate = .3,
  prevalence = .01
)

# Adding a small-world population
agents_smallworld(model_logit, n, 8, FALSE, .01)

# Running the model
run(model_logit, 50)
#> _________________________________________________________________________
#> |Running the model...
#> |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| done.
#> | done.
plot(model_logit)


# Females are supposed to be more likely to become infected
rn <- get_reproductive_number(model_logit)

(table(
  X[, "Female"],
  (1:n %in% rn$source)
) |> prop.table())[, 2]
#>       0       1
#> 0.12984 0.14201

# Looking into the agents
get_agents(model_logit)
#> Agents from the model "Susceptible-Infected-Removed (SIR) (logit)":
#> Agent: 0, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 1, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 2, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 3, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 4, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 5, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 6, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 7, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 8, state: Susceptible (0), Has virus: no, NTools: 0i NNeigh: 8
#> Agent: 9, state: Recovered (2), Has virus: no, NTools: 0i NNeigh: 8
#> ... 99990 more agents ...

Transmission network

This example shows how we can draw a transmission network from a simulation. The following code simulates a population of 500 agents in a small-world network. Each agent is connected to ten other agents. One percent of the population has the virus, with a 50% chance of transmission. Infected individuals recover at a 0.5 rate:

# Creating a SIR model
sir <- ModelSIR(
  name           = "COVID-19",
  prevalence     = .01,
  transmission_rate = .5,
  recovery       = .5
) |>
  # Adding a Small world population
  agents_smallworld(n = 500, k = 10, d = FALSE, p = .01) |>
  # Running the model for 50 days
  run(ndays = 50, seed = 1912)
#> _________________________________________________________________________
#> |Running the model...
#> |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| done.
#> | done.

# Transmission network
net <- get_transmissions(sir)

# Plotting
library(epiworldR)
library(netplot)
#> Loading required package: grid
x <- igraph::graph_from_edgelist(
  as.matrix(net[, 2:3]) + 1
)

nplot(x, edge.curvature = 0, edge.color = "gray", skip.vertex = TRUE)

Multiple simulations

epiworldR supports running multiple simulations using the run_multiple function. The following code simulates 50 SIR models with 1000 agents each. Each agent is connected to ten other agents. One percent of the population has the virus, with a 90% chance of transmission. Infected individuals recover at a 0.1 rate. The results are saved in a data.frame:

model_sir <- ModelSIRCONN(
  name = "COVID-19",
  prevalence = 0.01,
  n = 1000,
  contact_rate = 2,
  transmission_rate = 0.9, recovery_rate = 0.1
)

# Generating a saver
saver <- make_saver("total_hist", "reproductive")

# Running and printing
# Notice the use of nthread = 2 to run the simulations in parallel
run_multiple(model_sir, ndays = 100, nsims = 50, saver = saver, nthread = 2)
#> Starting multiple runs (50)
#> _________________________________________________________________________
#> _________________________________________________________________________
#> ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| done.
#>  done.

# Retrieving the results
ans <- run_multiple_get_results(model_sir)

head(ans$total_hist)
#>   sim_num date nviruses       state counts
#> 1       1    0        1 Susceptible    990
#> 2       1    0        1    Infected     10
#> 3       1    0        1   Recovered      0
#> 4       1    1        1 Susceptible    971
#> 5       1    1        1    Infected     29
#> 6       1    1        1   Recovered      0
head(ans$reproductive)
#>   sim_num virus_id    virus source source_exposure_date rt
#> 1       1        0 COVID-19    943                    9  0
#> 2       1        0 COVID-19     40                    9  0
#> 3       1        0 COVID-19      6                    9  0
#> 4       1        0 COVID-19    973                    8  0
#> 5       1        0 COVID-19    495                    9  0
#> 6       1        0 COVID-19    480                    8  0

plot(ans$reproductive)

Tutorials

Citation

If you use epiworldR in your research, please cite it as follows:

citation("epiworldR")
#> To cite epiworldR in publications use:
#>
#>   Meyer, Derek and Vega Yon, George (2023). epiworldR: Fast Agent-Based
#>   Epi Models. Journal of Open Source Software, 8(90), 5781,
#>   https://doi.org/10.21105/joss.05781
#>
#> And the actual R package:
#>
#>   Meyer D, Vega Yon G (????). _epiworldR: Fast Agent-Based Epi Models_.
#>   R package version 0.3-2, <https://github.com/UofUEpiBio/epiworldR>.
#>
#> To see these entries in BibTeX format, use 'print(<citation>,
#> bibtex=TRUE)', 'toBibtex(.)', or set
#> 'options(citation.bibtex.max=999)'.

Existing Alternatives

Several alternatives to epiworldR exist and provide researchers with a range of options, each with its own unique features and strengths, enabling the exploration and analysis of infectious disease dynamics through agent-based modeling. Below is a manually curated table of existing alternatives, including ABM [@ABM], abmR [@abmR], cystiSim [@cystiSim], villager [@villager], and RNetLogo [@RNetLogo].

Package Multiple Viruses Multiple Tools Multiple Runs Global Actions Built-In Epi Models Dependencies Activity
epiworldR yes yes yes yes yes status Activity
ABM - - - yes yes status Activity
abmR - - yes - - status Activity
cystiSim - yes yes - - status Activity
villager - - - yes - status Activity
RNetLogo - yes yes yes - status Activity

Other ABM R packages

You may want to check out other R packages for agent-based modeling: ABM, abmR, cystiSim, villager, and RNetLogo.

Code of Conduct

The epiworldR project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.