When I use the Symbolic Math Toolbox, I get results like abs(1,x). I would like to know what it means.
Best Answer
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.
It happens because for the scalar case norm(y)=|y| (here y=y(x) is any function), therefore Matlab computes derivative by splitting the two cases in the derivative of|y|: y>=0 and y<0. Then it combines the results in a signle function by the sign*|.| trick.
That is true, but it doesn't imply that x you declared will have abs as its method.
I think that claim you quoted means that MATLAB's data types are internally implemented as object-oriented classes. The double data type doesn't provide any method.
Best Answer