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SciMax Toolbox >> genmatrix

genmatrix

Maxima Function

Calling Sequence

genmatrix (a, i_2, j_2, i_1, j_1)
genmatrix(a,i_2,j_2,i_1)
genmatrix(a,i_2,j_2)

Description

Returns a matrix generated from a, taking element a[i_1,j_1] as the upper-left element and a[i_2,j_2] as the lower-right element of the matrix. Here a is a declared array (created by array but not by make_array) or an undeclared array, or an array function, or a lambda expression of two arguments. (An array function is created like other functions with := or define, but arguments are enclosed in square brackets instead of parentheses.)

If j_1 is omitted, it is assumed equal to i_1. If both j_1 and i_1 are omitted, both are assumed equal to 1.

If a selected element i,j of the array is undefined, the matrix will contain a symbolic element a[i,j].

Examples:

(%i1) h [i, j] := 1 / (i + j - 1);
                                    1
(%o1)                  h     := ---------
                        i, j    i + j - 1
(%i2) genmatrix (h, 3, 3);
                           [    1  1 ]
                           [ 1  -  - ]
                           [    2  3 ]
                           [         ]
                           [ 1  1  1 ]
(%o2)                      [ -  -  - ]
                           [ 2  3  4 ]
                           [         ]
                           [ 1  1  1 ]
                           [ -  -  - ]
                           [ 3  4  5 ]
(%i3) array (a, fixnum, 2, 2);
(%o3)                           a
(%i4) a [1, 1] : %e;
(%o4)                          %e
(%i5) a [2, 2] : %pi;
(%o5)                          %pi
(%i6) genmatrix (a, 2, 2);
                           [ %e   0  ]
(%o6)                      [         ]
                           [ 0   %pi ]
(%i7) genmatrix (lambda ([i, j], j - i), 3, 3);
                         [  0    1   2 ]
                         [             ]
(%o7)                    [ - 1   0   1 ]
                         [             ]
                         [ - 2  - 1  0 ]
(%i8) genmatrix (B, 2, 2);
                        [ B      B     ]
                        [  1, 1   1, 2 ]
(%o8)                   [              ]
                        [ B      B     ]
                        [  2, 1   2, 2 ]
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