linalg
::expr2Matrix
Construct a matrix from equations
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linalg::expr2Matrix(eqns
, <vars, R
>, <Include>)
linalg::expr2Matrix(eqns, vars)
constructs
the extended coefficient matrix of the system
of m linear
equations in eqns
with respect to the n indeterminates
in vars
. The vector is the righthand
side of this system.
linalg::expr2Matrix
returns the extended
coefficient matrix . The righthand
side vector can be extracted
from the matrix M by linalg::col
(M,
n + 1)
.
The coefficient matrix A can
be extracted by linalg::delCol
(M, n + 1)
.
Arithmetical expressions in eqns
are considered
as equations with right handsides zero.
If no variables are given, then the indeterminates of the equations
are determined with the function indets
and the option PolyExpr
,
i.e., the lefthand sides of the equations are considered as polynomial
expressions.
If no component ring R
is given then the
standard domain Dom::ExpressionField
()
is chosen as the
component ring of the extended coefficient matrix.
The coefficients of the linear equations are converted into
elements of the component ring R
. An error message
is returned if this is not possible.
The extended coefficient matrix of the system x + y + z = 1, 2 y  z + 5 = 0 of linear equations in the variables x, y, z is the following 2×4 matrix:
delete x, y, z: Ab := linalg::expr2Matrix( [x + y + z = 1, 2*y  z + 5], [x, y, z], Dom::Real )
We use linalg::matlinsolve
to compute the general
solution of this system:
linalg::matlinsolve(Ab)
The coefficient matrix or the righthand side vector can be
be extracted from the matrix Ab
in the following
way:
A := linalg::delCol(Ab, 4); b := linalg::col(Ab, 4)
The following two inputs lead to different linear systems:
delete x, y, z: linalg::expr2Matrix([x + y + z = 1, 2*y  z + 5 = x]), linalg::expr2Matrix([x + y + z = 1, 2*y  z + 5 = x], [x, y])
Note the difference between calling linalg::expr2Matrix
with
and without option Include
:
delete x, y: linalg::expr2Matrix([x + y = 1, 2*x  y = 3], [x, y])
linalg::expr2Matrix([x + y = 1, 2*x  y = 3], [x, y], Include)

The system of linear equations, i.e. a set or list of expressions
of type 

A set or list of indeterminates 

A commutative ring, i.e., a domain of category 

Appends the negative of the righthand side vector to the coefficient matrix A of the given system of linear equations. The result is the m×(n + 1) matrix . 
m×(n +
1) matrix of the domain Dom::Matrix
(R)
.