Mercurial > forge
changeset 2712:f2a17922a667 octave-forge
Initial commit into CVS.
author | sis-sou |
---|---|
date | Tue, 17 Oct 2006 11:22:36 +0000 |
parents | 2e4ce287a594 |
children | e69a683bfcf5 |
files | main/specfun/inst/Ci.m |
diffstat | 1 files changed, 37 insertions(+), 0 deletions(-) [+] |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/main/specfun/inst/Ci.m Tue Oct 17 11:22:36 2006 +0000 @@ -0,0 +1,37 @@ +## Copyright (C) 2006 Sissou <sylvain.pelissier@gmail.com> +## +## This program is free software; you can redistribute it and/or modify +## it under the terms of the GNU General Public License as published by +## the Free Software Foundation; either version 2 of the License, or +## (at your option) any later version. +## +## This program is distributed in the hope that it will be useful, +## but WITHOUT ANY WARRANTY; without even the implied warranty of +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +## GNU General Public License for more details. +## +## You should have received a copy of the GNU General Public License +## along with this program; if not, write to the Free Software +## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + +## CI compute the cosine integral function define by: +## +## Inf +## / +## Ci(x) = | cos(t)/t dt +## / +## x +## +##See also : cosint, Si, sinint, expint, expint_Ei. + +function y = Ci(z) + if (nargin != 1) + usage ("Ci(x)"); + endif + y = z; + y(z == 0) = -Inf; + y(real(z) == 0 & imag(z) >0) = 0.5*(expint_Ei(i.*y(real(z) == 0 & imag(z) >0))+expint_Ei(-i.*y(real(z) == 0 & imag(z) >0)))+ i.*pi./2; + y(real(z) == 0 & imag(z) <0) = 0.5*(expint_Ei(i.*y(real(z) == 0 & imag(z) <0))+expint_Ei(-i.*y(real(z) == 0 & imag(z) <0)))-i*pi./2; + y(real(z)>0) = -0.5.*(expint_E1(i.*y(real(z)>=0) )+expint_E1(-i.*y(real(z)>=0) )); + y(real(z)<0) = -0.5.*(expint_E1(-i.*y(real(z)<0))+expint_E1(i.*y(real(z)<0)))+i*pi; +endfunction; \ No newline at end of file