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D.15.8.5 laxfrX

Procedure from library finitediff.lib (see finitediff_lib).

Usage:
laxfrX(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 Lax-Friedrich-approximation for the derivation in one of the spatial variables as often used in literature;

Note:
see also laxfrT, setinitials, scheme; Warning: laxfrX is not to be interchanged with laxfrT

Example:
 
LIB "finitediff.lib";
list D="Ux","Ut","U";
list P="a";
list V="t","x";
setinitials(V,D,P);
laxfrX(Ux,U,x);
==> [(2*dx)*x,0,-x^2+1]