readsdr

Overview

The goal of readsdr is to bridge the design capabilities from specialised System Dynamics software with the powerful numerical tools offered by R libraries. The package accomplishes this goal by parsing .xmile files (Vensim and Stella models) into R objects to construct networks (graph theory), ODE functions for deSolve and Stan.

Installation

You can install the released version of readsdr from CRAN with:

install.packages("readsdr")

And the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("jandraor/readsdr")

Usage

library(readsdr)
filepath <- system.file("models/", "SIR.stmx", package = "readsdr")
mdl      <- read_xmile(filepath) 
summary(mdl)
#>                    Length Class  Mode
#> description        4      -none- list
#> deSolve_components 4      -none- list
#> graph_dfs          2      -none- list

For reading Vensim models, they must be exported as .xmile.

For information on how to use this package, see the vignette or type vignette("Introduction_to_readsdr") in R.

Supported builtins

• Stella
  • Comparison operators (=, <>)
  • Logical operators (AND, OR, NOT)
  • If Else Then
  • Inequality operators (<, >)
  • Pulse ¹
  • Step ¹
  • Endogenous table functions
  • Smoothing functions: SMTH1, SMTH3, SMTHN
  • Limited support to uni-dimensional arrays. Apply all translation is restricted to numeric values.
  • Math functions: ABS, SQRT
  • Stats functions: NORMAL
• Vensim
  • Comparison operators (=, <>)
  • Logical operators (:AND:, :OR:, :NOT:)
  • IF_THEN_ELSE
  • Inequality operators (<, >)
  • Pulse ¹
  • Pulse Train ¹
  • Step ¹
  • Endogenous table functions
  • Smoothing functions: SMOOTH, SMOOTH3, SMOOTH3I, SMOOTHI
  • Math functions: ABS, SQRT

¹ Restricted to Euler integration.

Notes

• uniflow and non-negative stock features from Stella are not supported.

• No built-in is supported for translations to Stan code.

• Modules from Stella are not supported.

Acknowledgments

Thanks to:

• Rogelio Oliva for advocating the need to create an open-source tool for the System Dynamics community and push forward this endeavour.
• Sergey Naumov for his ideas to implement several functions in this package.
• Jim Duggan from whom I borrowed ideas to implement this package.

References

Duggan, J. (2016). System Dynamics Modeling with R. Springer.