Polynomial Anonymous function degree

How can I find the degree of a given "anonymous function" like f=@(x) x^2+2x; given the functions are only polynomials?

[dpb]

Convert to string via func2str and regexp() to return powers of exponentials--find max thereof. Of course, that presumes someone doesn't write a function like using the explicit form of Horner's rule--

f=@(x) (x+2).*x;

in which case you've got more work to do... :)

Answer 1

[Walter Roberson]

Build a vector

 X = realmax.^(1./(1:50));
 

Evaluate the function at X. The first result that is finite is probably the degree. However, it is possible for a polynomial with sufficiently large coefficients to generate an infinity "early", or for with sufficiently small leading coefficient to be "late" relative to this, so you should use that as a starting point to do more cross-checking.

[Ashish Sahu]

Thanks, it seems to work.

[Ashish Sahu]

This method doesn't seem to work for degree 4 & degree 5 polynomials.

f=@(x) x^4;

X = realmax.^(1./(1:50));

for i=1:50

Y = f(X(i));

if Y<Inf

break

end

end

degree = i % degree of polynomial is degree

I am getting degree = 5.

[Walter Roberson]

x^4 is a leading coefficient of 1 which is "suffiently small" in terms of what I wrote above.

Perhaps a slightly different X would help? You should analyze why this case fails to figure out what changes to make.