SD DSL Functions
system dynamics, systemdynamics, sd dsl, bptk, bptk-py, python, business simulation
SD DSL Functions
The SD DSL comes with the builtins of XMILE and Stella as Python functions in sd_functions. Import them beside the Model class:
from BPTK_Py import Model
from BPTK_Py import sd_functions as sdThe functions are on two pages, each sorted from A to Z:
- Deterministic Functions - everything that gives the same result on every run: time, delays and smoothing, finance, lookups, rounding and mathematics
- Random Functions - drawing numbers from statistical distributions
The statistical functions - the random distributions, INVNORM and NORMALCDF - check their arguments, and so do SQRT, LN, LOG10, ARCSIN, ARCCOS, FACTORIAL, COMBINATIONS, PERMUTATIONS and DELAY. An argument a function does not accept, such as a negative stddev, gives NaN, and one [ERROR] names the element, the time and the values; it is printed as well as written to the log file, once per element and run. A NaN or an infinity that arrives as an argument gives NaN without a message: it comes from further up the model.
Three operations divide by zero: a / 0, a % 0 and 0 ** -n, which is 1 / 0ⁿ. All yield NaN plus one [ERROR] in the log per element, naming the time it first happens. The run goes on.