Syntax

   [v, f] = taudiff(step, x, fun, order)

Description

   Evaluates the derivative from an approximated function.

Input

   step  = evaluation step (double).
   x     = independent tau variable (itau object).
   fun   = function f(x) (char or double vector).
   order = derivative order (integer).

Output

   v    = v(x).
   f    = coefficients for the approximation diff('fun(x)', order).

Examples

   x = itau('LegendreP', [0 1], 5);
   [v, f] = taudiff(0.1, x, ''x^2-3*x+1'', 2); or:
   x = itau('LegendreP', [0 1], 5);
   [v, f] = taudiff(0.1, x, [-1/6 -1 1/6]', 2);
   In the first example the function is
   interpolated by orthogonal basis whereas in the second the coefficients
   are already provided.

See also

  taufred, tauint, taudiff.