desc: Mambo column description

s1, ..., sn: variable names

The function CoeffExtract returns a Mambo description with number of rows equal to the number of rows of its first argument and number of columns equal to the number of variable names.

The (i,j)-th element of the output equals the coefficient of the j-th variable in the i-th row of the first argument.

>Restart():
>DeclareObservers(A):
>DeclarePoints(A,P):
>DeclareTriads(a):
>DefineObservers(A,A,a):
>DefinePoints(A,P,a,q1,q2,q3):
>DeclareStates(q1,q2,q3):
>kde:=DiffTime({q1^2+q2^2+q3^2=0}) union {q1t=u1,q2t=u2}:
>kde:=solve(kde,{seq(cat(q,i,t),i=1..3)}):
>vel:=VelocityDescription([subs(kde,LinearVelocity(A,P))]);

$\mathrm{vel}:=\mathrm{table}\left(\left[\left(1,1\right)=\mathrm{table}\left(\left[1=\mathrm{table}\left(\left[''Triad''=a,''Coordinates''=\left[\begin{array}{c}\mathrm{u1}\\ \mathrm{u2}\\ -\frac{\mathrm{q1}\mathrm{u1}+\mathrm{q2}\mathrm{u2}}{\mathrm{q3}}\end{array}\right]\right]\right),''Type''=''Vector'',''Size''=1\right]\right),''Type''=''Description'',''Size''=\left[1,1\right]\right]\right)$

>CoeffExtract(vel,[u1,u2]);

$\mathrm{table}\left(\left[\left(1,2\right)=\mathrm{table}\left(\left[1=\mathrm{table}\left(\left[''Triad''=a,''Coordinates''=\left[\begin{array}{c}0\\ 1\\ -\frac{\mathrm{q2}}{\mathrm{q3}}\end{array}\right]\right]\right),''Type''=''Vector'',''Size''=1\right]\right),\left(1,1\right)=\mathrm{table}\left(\left[1=\mathrm{table}\left(\left[''Triad''=a,''Coordinates''=\left[\begin{array}{c}1\\ 0\\ -\frac{\mathrm{q1}}{\mathrm{q3}}\end{array}\right]\right]\right),''Type''=''Vector'',''Size''=1\right]\right),''Type''=''Description'',''Size''=\left[1,2\right]\right]\right)$