Revising Matrices

Rows , columns , or a block of rows or columns can be deleted from a matrix.

$\blacktriangleright$ To delete (a block of) rows or columns

1.
Select a block of rows or columns by using the mouse.

2.
Press DEL.

$\blacktriangleright$ To add rows or columns of entries

1.
Select the matrix by placing the insertion point at the right of the matrix.

2.
From the Edit menu, choose Insert Rows or Insert Columns.

3.
Make appropriate choices from the dialog box that appears.


Tip    In the special case of a vector represented as an n×1 or 1×n matrix, you can lengthen the vector by placing the insertion point in the last input box and pressing ENTER. You can shorten a vector by placing the insertion point in the last input box and pressing BACKSPACE. You can start with a display box, or the input boxes that appear with the fraction, radical, or bracket buttons, and make the same kinds of changes.

$\blacktriangleright$ To change the alignment of entries

1.
Select the matrix using the mouse (or starting with the insertion point at the left of the matrix, press SHIFT + RIGHT ARROW).

2.
Click the Properties buttonitbpF0.3009in0.3009in0.0701inproperty.wmf.

3.
Make appropriate choices from the dialog box that appears.


You can replace a rectangular block in an existing matrix using Fill Matrix.

$\blacktriangleright$ To change a matrix with Fill Matrix

1.
Select a rectangular portion of the matrix by using the mouse.

2.
Click the Fill Matrix button, or from the Matrices submenu, choose Fill Matrix.

3.
Choose one of the items from the dialog box.

4.
Click OK.

The selected region of the matrix is filled with the entries that you chose.



\begin{example}
To change the lower-right $2\times 2$\ corner of the matrix
\...
... & 0 & 0 \\
7 & 0 & 0
\end{array}
\right]
\end{displaymath}
\end{example}

The lower-right corner is replaced by the 2×2 zero matrix. No new matrix is created.


You can delete a block of entries in a matrix by selecting a rectangular portion of the matrix with the mouse, and pressing DEL.



\begin{example}
To delete the entries in the lower-right $2\times 2$\ corner of...
... \Box & \Box
\end{array}
\right]
\end{displaymath}
\bigskip
\end{example}