getPowerDeriv

function dxp=getPowerDeriv(x,p,k)
 The k-th derivative of x^p

 INPUTS
    x: base
    p: power
    k: derivative order

 OUTPUTS
    dxp: k-th derivative of x^p

 SPECIAL REQUIREMENTS
    none

0001 function dxp=getPowerDeriv(x,p,k)
0002 %function dxp=getPowerDeriv(x,p,k)
0003 % The k-th derivative of x^p
0004 %
0005 % INPUTS
0006 %    x: base
0007 %    p: power
0008 %    k: derivative order
0009 %
0010 % OUTPUTS
0011 %    dxp: k-th derivative of x^p
0012 %
0013 % SPECIAL REQUIREMENTS
0014 %    none
0015 
0016 % Copyright (C) 2011 Dynare Team
0017 %
0018 % This file is part of Dynare.
0019 %
0020 % Dynare is free software: you can redistribute it and/or modify
0021 % it under the terms of the GNU General Public License as published by
0022 % the Free Software Foundation, either version 3 of the License, or
0023 % (at your option) any later version.
0024 %
0025 % Dynare is distributed in the hope that it will be useful,
0026 % but WITHOUT ANY WARRANTY; without even the implied warranty of
0027 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0028 % GNU General Public License for more details.
0029 %
0030 % You should have received a copy of the GNU General Public License
0031 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
0032 
0033 if (abs(x) < 1e-12) && (p > 0) && (k >= p) && (abs(p - round(p)) < 1e-12)
0034     dxp = 0;
0035 else
0036     dxp = x^(p-k);
0037     for i=0:k-1
0038         dxp = dxp*p;
0039         p = p-1;
0040     end
0041 end
0042 end