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4.2 Matrix Parts

Command: rank matrix

The rank of matrix is the maximal number of linearly independent columns of matrix, which is always equalt to the maximal number of linearly independent rows of matrix.

e13 : rank([[0,0],[0,0]]);

e13: 0

e14 : rank([[0,0],[0,1]]);

e14: 1

e15 : rank([[2,0],[0,1]]);

e15: 2

e17 : rank([[b,c],[0,a]]);

e17: 2

e18 : rank([[b,c,d],[a,0,a],[e,f,a]]);

e18: 3
Command: row matrix i

The command row returns the ith row of the matrix matrix, where i = int. If int is larger than the number of rows of matrix, then Jacal prints an error message. The corresponding command for columns of a matrix is col.

e3 : u:[[1, 2, 3], [1, 5, 3]];

    [1  2  3]
e3: [       ]
    [1  5  3]

e4 : row(u, 2);

e4: [1, 5, 3]
Command: col matrix integer

The command col is used to extract a column of a matrix. Here, matrix is a matrix and integer is a positive integer. If that integer exceeds the number of columns, an error message such as

ERROR: list-ref: Wrong type in arg1 ()

appears. Here is an example of correct use of the command col:

e19 : a:[[1,2,4],[2,5,6]];

     [1  2  4]
e19: [       ]
     [2  5  6]

e20 : col(a,2);

e20: [ ]
Command: minor matrix i j

The command minor returns the submatrix of matrix obtained by deleting the ith row and the jth column.

e21 : b:[[1,2,3],[3,1,5],[5,2,7]];

     [1  2  3]
     [       ]
e21: [3  1  5]
     [       ]
     [5  2  7]

e22 : minor(b,3,1);

     [2  3]
e22: [    ]
     [1  5]
Command: cofactor matrix i j

The command cofactor returns the determinant of the i, j minor of matrix.

Command: rapply bunch int_1 int_2 …

The function rapply is used to access elements of bunches. It can also access elements nested at lower levels in a bunch. In particular, it can also access matrix elements. In the above syntax, bunch is the bunch whose parts one wishes to access, and n, int_1, int_2, …, int_n are positive integers. It returns the int_n-th element of the int_{n-1}-th element of … of the int_2-th element of the int_1-th element of bunch. One can have n = 0. In that case, rapply simply returns the bunch.

e2 : rapply([[1,2,3],[1,4,6],3],2,3);

e2: 6

e6 : rapply([a,b],2);

e6: b

e7 : rapply([a,b]);

e7: [a, b]

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