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D.15.4.7 backward
Procedure from library finitediff.lib (see finitediff_lib).
- Usage:
- backward(U1,U2,var); U1, U2 are the names of occuring derivatives, var is a variable in the basering;
- Return:
- type vector; gives a predefined approximation of the backward approximation as often used in literature;
- Note:
- see also forward,laxfrT,setinitials,scheme;
Example:
| | LIB "finitediff.lib";
list D="Ut","Ux","Uy","U";
list V="t","x","y";
list P="a","b";
setinitials(V,D,P);
backward(Ux,U,x);
==> [0,(dx)*x,0,-x+1]
backward(Uy,U,y);
==> [0,0,(dy)*y,-y+1]
backward(Ut,U,t);
==> [(dt)*t,0,0,-t+1]
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