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D.15.4.12 pyramid
Procedure from library finitediff.lib (see finitediff_lib).
- Usage:
- pyramid(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 pyramid-approximation as often used in literature;
- Note:
- see also forward,laxfrT,setinitials,scheme;
Example:
| | LIB "finitediff.lib";
list D="Uxx","Ux","Utt","Ut","U";
list P="lambda";
list V="t","x";
setinitials(V,D,P);
pyramid(Ux,U,x);
==> [0,(dx)/3*x^2+(dx)/3*x+(dx)/3,0,0,-x^3+x]
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