[u,idmn,i,j,uxxx,uxxxx]=dx(u,idmn,i,j,uxxx,uxxxx);

function [u,idmn,i,j,uxxx,uxxxx]=dx(u,idmn,i,j,uxxx,uxxxx);

global splpcm_5; if isempty(splpcm_5), splpcm_5=0; end;
global splpcm_6; if isempty(splpcm_6), splpcm_6=0; end;
global splpcm_7; if isempty(splpcm_7), splpcm_7=0; end;
global splpcm_8; if isempty(splpcm_8), splpcm_8=0; end;
global splpcm_15; if isempty(splpcm_15), splpcm_15=0; end;
global splpcm_19; if isempty(splpcm_19), splpcm_19=0; end;
global splpcm_16; if isempty(splpcm_16), splpcm_16=0; end;
global splpcm_20; if isempty(splpcm_20), splpcm_20=0; end;
global splpcm_17; if isempty(splpcm_17), splpcm_17=0; end;
global splpcm_18; if isempty(splpcm_18), splpcm_18=0; end;
global splpcm_11; if isempty(splpcm_11), splpcm_11=0; end;
global splpcm_13; if isempty(splpcm_13), splpcm_13=0; end;
global splpcm_3; if isempty(splpcm_3), splpcm_3=0; end;
global splpcm_1; if isempty(splpcm_1), splpcm_1=0; end;
global splpcm_2; if isempty(splpcm_2), splpcm_2=0; end;
global splpcm_4; if isempty(splpcm_4), splpcm_4=0; end;
global splpcm_9; if isempty(splpcm_9), splpcm_9=0; end;
global splpcm_12; if isempty(splpcm_12), splpcm_12=0; end;
global splpcm_10; if isempty(splpcm_10), splpcm_10=0; end;
global splpcm_14; if isempty(splpcm_14), splpcm_14=0; end;
%***BEGIN PROLOGUE  DX
%***SUBSIDIARY
%***PURPOSE  Subsidiary to SEPELI
%***LIBRARY   SLATEC
%***TYPE      SINGLE PRECISION (DX-S)
%***AUTHOR  (UNKNOWN)
%***DESCRIPTION
%
%     This program computes second order finite difference
%     approximations to the third and fourth X
%     partial derivatives of U at the (I,J) mesh point.
%
%***SEE ALSO  SEPELI
%***ROUTINES CALLED  (NONE)
%***COMMON BLOCKS    SPLPCM
%***REVISION HISTORY  (YYMMDD)
%   801001  DATE WRITTEN
%   891214  Prologue converted to Version 4.0 format.  (BAB)
%   900402  Added TYPE section.  (WRB)
%***end PROLOGUE  DX
%
% common :: ;
%% common /splpcm/ kswx , kswy , k , l , ait , bit , cit , dit ,mit , nit , is , ms , js , ns , dlx , dly ,tdlx3 , tdly3 , dlx4 , dly4;
%% common /splpcm/ splpcm_1 , splpcm_2 , splpcm_3 , splpcm_4 , splpcm_5 , splpcm_6 , splpcm_7 , splpcm_8 ,splpcm_9 , splpcm_10 , splpcm_11 , splpcm_12 , splpcm_13 , splpcm_14 , splpcm_15 , splpcm_16 ,splpcm_17 , splpcm_18 , splpcm_19 , splpcm_20;
u_shape=size(u);u=reshape([u(:).',zeros(1,ceil(numel(u)./prod([idmn])).*prod([idmn])-numel(u))],idmn,[]);
%***FIRST EXECUTABLE STATEMENT  DX
if( i>2 && i<(splpcm_3-1) )
%
%     COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS ON THE INTERIOR
%
uxxx =(-u(i-2,j)+2.0.*u(i-1,j)-2.0.*u(i+1,j)+u(i+2,j))./splpcm_17;
uxxxx =(u(i-2,j)-4.0.*u(i-1,j)+6.0.*u(i,j)-4.0.*u(i+1,j)+u(i+2,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
else;
if( i~=1 )
if( i==2 )
%
%     COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=A+DLX
%
if( splpcm_1==1 )
%
%     PERIODIC AT X=A+DLX
%
uxxx =(-u(splpcm_3-1,j)+2.0.*u(1,j)-2.0.*u(3,j)+u(4,j))./(splpcm_17);
uxxxx =(u(splpcm_3-1,j)-4.0.*u(1,j)+6.0.*u(2,j)-4.0.*u(3,j)+u(4,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
else;
uxxx =(-3.0.*u(1,j)+10.0.*u(2,j)-12.0.*u(3,j)+6.0.*u(4,j)-u(5,j))./splpcm_17;
uxxxx =(2.0.*u(1,j)-9.0.*u(2,j)+16.0.*u(3,j)-14.0.*u(4,j)+6.0.*u(5,j)-u(6,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
end;
elseif( i==splpcm_3-1 ) ;
%
%     COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=B-DLX
%
if( splpcm_1==1 )
%
%     PERIODIC AT X=B-DLX
%
uxxx =(-u(splpcm_3-3,j)+2.0.*u(splpcm_3-2,j)-2.0.*u(1,j)+u(2,j))./splpcm_17;
uxxxx =(u(splpcm_3-3,j)-4.0.*u(splpcm_3-2,j)+6.0.*u(splpcm_3-1,j)-4.0.*u(1,j)+u(2,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
else;
uxxx =(u(splpcm_3-4,j)-6.0.*u(splpcm_3-3,j)+12.0.*u(splpcm_3-2,j)-10.0.*u(splpcm_3-1,j)+3.0.*u(splpcm_3,j))./splpcm_17;
uxxxx =(-u(splpcm_3-5,j)+6.0.*u(splpcm_3-4,j)-14.0.*u(splpcm_3-3,j)+16.0.*u(splpcm_3-2,j)-9.0.*u(splpcm_3-1,j)+2.0.*u(splpcm_3,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
end;
elseif( i==splpcm_3 ) ;
%
%     COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=B
%
uxxx = -(3.0.*u(splpcm_3-4,j)-14.0.*u(splpcm_3-3,j)+24.0.*u(splpcm_3-2,j)-18.0.*u(splpcm_3-1,j)+5.0.*u(splpcm_3,j))./splpcm_17;
uxxxx =(-2.0.*u(splpcm_3-5,j)+11.0.*u(splpcm_3-4,j)-24.0.*u(splpcm_3-3,j)+26.0.*u(splpcm_3-2,j)-14.0.*u(splpcm_3-1,j)+3.0.*u(splpcm_3,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
end;
end;
%
%     COMPUTE PARTIAL DERIVATIVE APPROXIMATIONS AT X=A
%
if( splpcm_1==1 )
%
%     PERIODIC AT X=A
%
uxxx =(-u(splpcm_3-2,j)+2.0.*u(splpcm_3-1,j)-2.0.*u(2,j)+u(3,j))./(splpcm_17);
uxxxx =(u(splpcm_3-2,j)-4.0.*u(splpcm_3-1,j)+6.0.*u(1,j)-4.0.*u(2,j)+u(3,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
else;
uxxx =(-5.0.*u(1,j)+18.0.*u(2,j)-24.0.*u(3,j)+14.0.*u(4,j)-3.0.*u(5,j))./(splpcm_17);
uxxxx =(3.0.*u(1,j)-14.0.*u(2,j)+26.0.*u(3,j)-24.0.*u(4,j)+11.0.*u(5,j)-2.0.*u(6,j))./splpcm_19;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
return;
end;
end;
u_shape=zeros(u_shape);u_shape(:)=u(1:numel(u_shape));u=u_shape;
end
%DECK DXLCAL