How to calculate the derivate of an equation ?

Hi All

I have the crack energy equation :

In which R and G are numbers , also c and m. N is loading cycle : so it's a signal.

in which rho is defined as :

Having the second equation, how can I derivate it with respect to N numerically ?

Answer 1

[Star Strider]

To calculate a numerical derivative of a vector, use the gradient function.

If ‘N’ is a vector, use gradient on it, then multiply that result by the other term in the expression.

[farzad]

Thank you very much! Is gradient equivalent for derivative? Are they the same in math?

[Star Strider]

My pleasure!

The MATLAB gradient function calculates the central difference approximation of the numerical derivative. Mathematically, Gradient is a specific term that the gradient function actually creates with a matrix argument. With a vector, the MATLAB gradient function returns the derivative of the vector. See the documentation for a full description of the function and its use.