Algorithm (Workflow)

This function, subsvar, is designed to substitute multiple symbols or terms in a symbolic equation. It is part of the SYMBOLICS TOOLS class and was introduced in SolidGeometry 4.2.

Input Parameters

• f: The original term or equation that you want to modify.
• sv: An array of symbols to substitute. It can be a simple list of symbols or a matrix where the first column contains symbols and the second column contains their corresponding values.
• varargin: An optional parameter that can be used to specify new values for the symbols in sv.

Output Results

• g: The resulting term or equation after substitution.

Algorithm Steps

1. Initialize an empty array nv.
2. Check if there are at least three input arguments and if the third argument is not empty. If so, assign it to nv.
3. If there are fewer than three arguments, assume sv is a matrix with symbols in the first column and values in the second. Assign these to sv and nv respectively.
4. Initialize g with the original equation f.
5. Iterate over each symbol in sv and substitute it with the corresponding value in nv using the subs function.
6. If no output is requested (i.e., nargout==0), display the result in a pretty format.

Example Usage

Consider the following example where syms x(t) D C F m; defines symbolic variables and dx=diff(x); ddx=diff(x,2); defines derivatives. The function dsolve is used to solve a differential equation, and subsvar is used to substitute values for D and m.

Example code:

syms x(t) D C F m; 
dx=diff(x); 
ddx=diff(x,2);
f=dsolve(m*ddx+D*dx==0, x(0)==0,x(6)==1); 
sv=symvar(f);
subsvar(f,[D m],[1 1]);
subsvar(f,[D 1;m 1]);