What does abs(1,x) mean in MATLAB?

When I use the Symbolic Math Toolbox, I get results like abs(1,x). I would like to know what it means.

Answer 1

[MathWorks Support Team]

In maple, the derivative of abs is denoted by abs(1, x). This is signum(x) for all non-zero real numbers, and is undefined otherwise.

Higher order derivatives of abs are denoted by abs(n, x), where 'n' is a positive integer. When 'n' is known, the expression is automatically simplified to the appropriate expression in a derivative of either signum or abs.

For more information on this function, type:

mhelp abs

For example:

syms y

diff(abs(y),y);

returns the following:

 abs(1, y)