expression substitution

Hi, I would like to use regexprep to substitute a simple expression for another in a text.

As an example, I have the following expression A=g*ABC+(1-g)*(CAD+d*EEA)+ZI/A , and would like to replace all occurrences of the word A with A_subs. The result would be A_subs=g*ABC+(1-g)*(CAD+d*EEA)+ZI/A_subs . Could you suggest a simple call to regexprep that would do this? Thanks, Junior

[Friedrich]

So the ABC part has to stay and should not become A_subsBC?

[Junior]

Hi Friedrich, the answer to your question is yes.

Answer 1

[David Young]

s = 'A=g*ABC+(1-g)*(CAD+d*EEA)+ZI/A';
regexprep(s, '(^|\W)A($|\W)', '$1A_subs$2')

EDIT: See Walter Roberson's comment for a more elegant solution.

[Walter Roberson]

s = 'A=g*ABC+(1-g)*(CAD+d*EEA)+ZI/A';

regexprep(s, '(\<A\>)', '$1_subs')

[Oleg Komarov]

@Walter: very elegant.

[Andrei Bobrov]

Hi David, +1.

Hi Walter, super nice!

[David Young]

Hi Andrei: thanks.

Hi Walter: wish I'd spotted that!

Answer 2

[Andrei Bobrov]

char(subs('A = ABC*g + ZI/A - (CAD + EEA*d)*(g - 1)','A','A_subs'))

ADD MORE variant

str='A=g*ABC+(1-g)*(CAD+d*EEA)+ZI/A'
t = regexp(str,'A=|[*/-+=]+A+$|[*/-+=]+A+[*/-+=]')
str2 = mat2cell(str,1,[1 diff(t) 1])
str2(strcmp(str2,'A'))={'A_subs'}
strout = cell2mat(str2)

[Friedrich]

Little note: this works but requires Symbolic Math Toolbox.

[Junior]

Hi Andrei, thanks for the answer. It is precisely a problem with the symbolic math toolbox that brought me here. Try replacing "A" with "I" and you will see it does not work. I need to do some substitutions before passing the expression to the symbolic math toolbox.