Separate definition of constant values and dependent parameters in Matlab - matlab

Question

In my code, I have a lot of constant values and parameters that take significant space in my code.
For example in C++, I would make a header and a separate file where I would define these parameters as, e.g., "const-type" and share the header with main or other .cpp files.
How do you keep such structuring in MATLAB, is it worth it?
An example: Coefficients.m looks as follows:
classdef coefficients
properties(Constant)
% NIST data
A_N = 28.98641;
end
end
Another file: Gas.m where I would like to use A_N looks as follows:
function Gas()
clear all
clc
import Coefficients.* % Does not work
% A simple print
Values.A_N % Does not work
coefficients.A_N % Does not work
Constant.A_N % Does not work
end

Answer 1

Ok so assuming the class coefficients defined as:
classdef coefficients
properties(Constant)
% NIST data
A_N = 28.98641;
end
end
This code must be saved in a file named coefficients.m (The class name and file name have to match to avoid weird effect sometimes).
Then assuming the following Gas.m file:
function Gas()
% Usage with "disp()"
disp('The A_N coefficient taken from NIST data is:')
disp(coefficients.A_N)
% Usage with fprintf
fprintf('\nFrom NIST data, the coefficient A_N = %f\n',coefficients.A_N)
% Usage in calculation (just use it as if it was a variable/constant name
AN2 = coefficients.A_N^2 ;
fprintf('\nA_N coefficient squared = %.2f\n',AN2)
% If you want a shorter notation, you can copy the coefficient value in
% a variable with a shorter name, then use that variable later in code
A_N = coefficients.A_N ;
fprintf('\nA_N coefficient cubed = %.2f\n',A_N^3)
end
Then running this file (calling it from the command line) yields:
>> Gas
The A_N coefficient taken from NIST data is:
28.98641
From NIST data, the coefficient A_N = 28.986410
A_N coefficient squared = 840.21
A_N coefficient cubed = 24354.73
Or if you simply need to access the coefficient in the Matlab console:
>> coefficients.A_N
ans =
28.98641
Now all these examples assume that the class file coefficient.m is visible in the current Matlab scope. For Matlab, it means the file must be in the MATLAB search path (or the current folder works too).
For more info about what is the Matlab search path and how it works you can read:
What Is the MATLAB Search
Path?
Files and Folders that MATLAB
Accesses
In your case, I would make a folder containing all these sorts of classes, then add this folder to the Matlab path, so you never have to worry again about individual script, function or program calling for it.

Answer 2

See this link for tips on using a class definition for this. Highlights of the tips are:
Properties can be accessed directly to get the value
Properties can be added that give the units of the constant (highly advised!)
Comments can be added that act as help text for the constants
The doc command automatically creates a reference page for this classdef
E.g.,
classdef myconstants
properties(Constant)
% g is the gravity of Earth
% (https://en.wikipedia.org/wiki/Gravity_of_Earth)
g = 9.8;
g_units = 'm/s/s';
% c is the speed of light in a vacuum
c = 299792458;
c_units = 'm/s';
end
end
>> help myconstants.g