Creating a table from a matrix and two vectors

asked 2020-08-04 12:56:59 +0100

Cyrille gravatar image

updated 2020-08-04 17:33:13 +0100

slelievre gravatar image

Suppose I have the following matrix (8x4) matrix

$\begin{bmatrix} 1 & 2 & 3 & 4 & 1 & 0 & 0 & 20 \\ 1 & 4 & 5 & 4 & 0 & 1 & 0 & 10 \\ 2 & 2 & 3 & 4 & 1 & 0 & 1 & 30 \\ 1 & -1 & 2 & -1 & 0 & 0 & 0 & 0 \end{bmatrix}$

I want to create a table in adding the following vector above

$ \begin{bmatrix} &x_1 & x_2 & x_3 & x_4 & \epsilon_1 & \epsilon_2 & \epsilon_3 & b \end{bmatrix} $

which will be invariant

and the following column vector on its right

$ \begin{bmatrix} \epsilon_1 \\ \epsilon_2 \\ \epsilon_3 \\ b \end{bmatrix} $

Two answers to my previous question "Concatenation of symbolic vectors" help me construct the line vector which is a concatenation of two vectors. But I cannot use the answer in the table() mechanism simply because it doesn't work as expected that is

table(name_of_the_matrix, header_row=name_of_the_line_vector)

Is there a way to obtain what I expect? I observed that html.table() doesn't work.

edit retag flag offensive close merge delete

Comments

I edited the question to fix the formatting and removed your technical post-scriptum:

PS. I do not understand why the formatting doesn't work for the matrix.

To answer that: it is a technical issue with escape sequences and backslash characters.

Workaround: in LaTeX code between $ ... $, type \\ for \ and so \\\\ for\`.

This probably has to do with the MathJax configuration of the Askbot engine powering Ask Sage.

slelievre gravatar imageslelievre ( 2020-08-04 15:28:14 +0100 )edit

Starting input to get anyone started on an answer:

x = [SR.var(f'x_{i}', latex_name=f'x_{i}') for i in range(5)]
y = [SR.var(f'y_{i}', latex_name=f'\\epsilon_{i}') for i in range(4)]
b = SR.var('b')

a = matrix([[1,  2, 3,  4, 1, 0, 0, 20],
            [1,  4, 5,  4, 0, 1, 0, 10],
            [2,  2, 3,  4, 1, 0, 1, 30],
            [1, -1, 2, -1, 0, 0, 0,  0]])

u = vector(SR, x[1:] + y[1:] + [b])
v = vector(SR, y[1:] + [b])

Now all there is to do is to arrange a, u, v as in the question.

slelievre gravatar imageslelievre ( 2020-08-04 15:37:27 +0100 )edit

For reference it seems such tables are often used when applying the "simplex algorithm" (or "simplex method") and in that context they are sometimes called simplex tables.

slelievre gravatar imageslelievre ( 2020-08-04 18:51:13 +0100 )edit
add a comment