The array
environment is provided for typesetting arrays
and array-like material. It accepts two arguments, one optional
and one mandatory. The optional argument specifies the vertical
alignment of the array—use t
, b
, or c
to align
the top, bottom, or centre of the array with the centreline of the
line it occurs on (the default being c
). The second argument
is as for the tabular
environment: a series of l
,
r
, and c
's that specify the number of columns and the
justification of these columns. The body of the array
environment
uses the same syntax as the tabular
environment to specify
the individual entries of the array.
For instance the input
0.1
... let $A = \begin{array}{rrr} 12 & 3 & 4\\ -2 & 1 & 0\\ 3 & 7 & 9 \end{array}$ ...will produce the output
let
A =
Note that we had to choose and supply the enclosing brackets
ourselves (they are not placed for us so that we can use the
array
environment for array-like material; also,
we get to choose what type of brackets we want this way).
As in the tabular
environment, the scope of a command
given inside a matrix entry is restricted to that entry.
We can use ellipsis within arrays as in the following example:
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\det A = \left| \begin{array}{cccc} a_{11} & a_{12} & \cdots & a_{1n}\\ a_{21} & a_{22} & \cdots & a_{2n}\\ \vdots & \vdots & \ddots & \vdots\\ a_{m1} & a_{m2} & \cdots & a_{mn} \end{array} \right|which produces
det A =
The array
environment is often used to typeset material that
is not, strictly speaking, an array:
0.1
f(x) = \left\{ \begin{array}{ll} x & \mbox{for $x<1$}\\ x^2 & \mbox{for $x \geq 1$} \end{array} \right.which will yield
f (x) =