Any idea to convert numerics to symbolic ?

How can I convert an equation with the numeric coeffs to symbolic ?

example :

y= 2*exp(3*x)+log10(4*x+9)+10

so I get

y= a1*exp(a2*x)+log10(a3*x+a4)+a5

Answer 1

[Andreas Goser]

I can think of string operations. But you need to find rules how to smartly cover situations where you don't want to replace a number with a variable like in x.^2.

Answer 2

[Stephan Moeller]

yes, me too. But there isn't anything already available as a function ?

[Andreas Goser]

Don't think so. I never heard of such an operation. Instead of numerics to symbolic I would also rather call it "generalizing coefficients" or so. But exactly because if this difficulty to name it, it is also difficult to search for it. Lets see if more people reply.

[Stephan Moeller]

yeah, you're right ! Thanks :-)

Answer 3

[pietro]

You can use the symbolic toolbox. Here an example:

syms z,x

z=3*x; y=subs(z1,{3},{a})

With a workaround I think you can do what you need

[Stephan Moeller]

I meant without explizit writing all numerics maunally.

[pietro]

you can write your formula in symbolic way, then using symvar you can get the symboli variables:

y=2*exp(3*x)+log10(4*x+9)+10 Then with symvar you can get the variables.

symvar(y)

ans =

x

so you can get everything since operators and functions are known. After having got the numeric values, you can substitute them using subs

Hope this helps

Answer 4

[Andrei Bobrov]

x= 'a':'z';
z = '2*exp(3*x)+log10(4*x+9)+10';
dd = regexp(z,'(?<=[\(-*/+ ])\d*|\d*(?=[+*-/\)])','match');
out = regexprep(z,dd',cellstr(x(1:numel(dd))'));

[Stephan Moeller]

out = a*exp(b*x)+loge(c*x+d)+e

log10 is lost ...