symbolicToMdss

Method of stringParser.

Build an mdss model from symbolic or string equations.

Source: src/utilities/@stringParser/symbolicToMdss.m

Syntax

sys = stringParser.symbolicToMdss(eq, Ts)
sys = stringParser.symbolicToMdss(eq, Ts, symbols)
sys = stringParser.symbolicToMdss(eq, Ts, symbols, symbolicParameters, numericParameters)

Description

symbolicToMdss parses a set of equations into an mdss object, building the structure and parameter matrices and the signal index vectors automatically.

Each equation may be written in any form (0 = …, or a polynomial on both sides); it is rearranged into the implicit form 0 = h(…) internally. Multiplication must be explicit (a*x1, not a x1). Allowed operators are * + - / ^ and parentheses. Inequalities (>=, <=) become inequality rows.

Integer powers are supported: the parser introduces auxiliary algebraic variables and equations to reduce any power to a multilinear product (so x1^3 becomes a chain of products). Because powers are handled structurally, exponents cannot be identified as parameters.

Symbols

The third argument maps each variable role to its symbol prefix, in the order

[stateDelta, state, input, algebraic, binary]

with default ["xp", "x", "u", "y", "z"]. Different variables of one role are distinguished by an integer index (x1, x2, …). Any token that is not one of the role symbols is treated as a parameter.

You may supply fewer symbols: the list is taken as a prefix of the five roles and the missing trailing roles keep their defaults. For example ["xp","x"] parses a pure ODE system with no inputs, algebraic or binary variables.

Parameters

Symbolic parameters and their numeric values are passed inline as the fourth and fifth arguments; the returned model is then ready to simulate. Omitting them keeps the parameters symbolic (useful for inspection, but they must be replaced with numbers before simulation).

Input arguments

Argument	Description
`eq`	Equations as a string / symbolic array (or cell).
`Ts`	Sample time: `0` continuous-time, `>0` discrete-time.
`symbols`	(optional) role symbols, default `["xp","x","u","y","z"]`.
`symbolicParameters`	(optional) symbolic parameters to substitute.
`numericParameters`	(optional) numeric values, aligned with `symbolicParameters`.

Examples

Continuous-time model with named parameters supplied inline:

eq = ["xp1 = a*x2*x3"; ...
      "xp2 = x1 - b*x2"; ...
      "xp3 = c - x1*x2"];

sys = stringParser.symbolicToMdss( ...
        eq, 0, ["xp","x","u","y","z"], ...
        sym(["a","b","c"]), [0.4, 1.2, 1]);

Fewer symbols for a pure ODE (no inputs/algebraic/binary), leaving a parameter symbolic:

sys = stringParser.symbolicToMdss(["xp1 = x2"; "xp2 = -k*x1"], 0, ["xp","x"]);

Custom role symbols:

eq  = ["out1*in1 = x1*in3"; "xp1 = in1 - x1"];
sys = stringParser.symbolicToMdss(eq, 0, ["xp","x","in","out"]);