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D.15.6.13 setinitials
Procedure from library finitediff.lib (see finitediff_lib).
- Usage:
- setinitials(V,D[,P]); V,D,P are lists with strings as elements
- Return:
- no return value: sets the dependence order of the occuring derivatives,
constructs the suitable ring to compute in containing user chosen parameters, sets new basering
- Note:
- P is optional, used to introduce some additional parameters into the ring. The Sine and
Cosine values needed for the fourier transformation are symbolically introduced under the names
string(c)+nameof(variable), i.e. if x is any spatial variable then cx:=cosine(dx*ksi), when
regarding the fourier transform after ksi (for sine respectively). Artificial parameters I,T,Px,Py
are introduced for the later eigenvalue analysis. Variables can be transformed into parameters
of similar name
Example:
| | LIB "finitediff.lib";
list D="Ut","Ux","Uy","U";
list V="t","x","y";
list P="alpha","beta","gamma";
setinitials(V,D,P);////does not show the ring, since there is no output
basering;///does show the ring
==> // characteristic : 0
==> // 14 parameter : I T Px Py Cx Cy Sx Sy alpha beta gamma dt dx dy
==> // minpoly : 0
==> // number of vars : 8
==> // block 1 : ordering c
==> // block 2 : ordering lp
==> // : names i t x y cx cy sx sy
==> // quotient ring from ideal
==> _[1]=cy^2+sy^2-1
==> _[2]=cx^2+sx^2-1
==> _[3]=i^2+1
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