Matlab: Programatically replacing *_dot notation with diff(*,t) in symbolic equations

Question

I need to create a function that replaces all instances of variable_dot with diff(variable,t) in a given symbolic function. I don't want to tell the function which variables to look for, I want it to operate on anything that ends in _dot.

For example:

func = x_dot + y_dot

I want to call newFunc = convertFunction(func) to give

syms x(t) y(t);
newFunc = diff(x,t) + diff(y,t)

Has anybody performed similar, or can anybody point me towards the best approach to take?

Answer 1

You can use regular expressions:

s= 'func = x_dot + y_dot'
expr='\w+_dot'
new_s= regexprep(s,expr,'diff(${strrep($0,''_dot'','''')},t)')

Answer 2

Here's the solution I used, based on AVK's answer. While his method came close, I ran into problems converting between strings and symbolic equations in a valid manner. Excuse the use of eval, it was the quickest way I could think of achieving this, I'm more than open to improvements.

function [ newFunc ] = replaceDotNotation( func )

vars = symvar(func);
newFunc = func;

for i = 1:numel(vars)
    if endsWith(char(vars(i)), '_dot')
        expr ='\w+_dot';
        newVarName = regexprep(char(vars(i)),expr,'${strrep($0,''_dot'','''')}(t)');
        s = ['syms ', newVarName];
        eval(s);
        s = ['newVal = ', regexprep(char(vars(i)),expr,'diff(${strrep($0,''_dot'','''')},t)')];
        eval(s);
        newFunc = subs(newFunc, vars(i), newVal);
    end
end
end