HP 48G - Page 28

(MATRIX), (STAT) AnD (2]
Although its name seems so similar to the statistical
commands (such as Z0AT, £+ and £-), the & com-
mand (available via([>]£)) is notdirectly tied to statis-
tics; you can use & to sum any finite series.
Example: Sum the first k powers of 2 (2°+ 2! ... + 2%):
Enter 'N', then B, then 'K', then '2*N', and (©)Z);
or: Enter 'Z{N=H, A, 2*N}' —and you can use the
EquationWriter to do this. Any way you do it, it means
“Find the sum of 2" for all integers n from 0 to k.”*
Contrast that with the true statistics functions, which
all relate to the matrix (array) of data currently stored
in the reserved name ZDAT. Recall that an array can
contain either real or complex values (see page 1),
and that you can enter an array on the stack directly
viathe [[ 1] syntax.** Butthere’s also a special tool
for easy matrix entry and editing:
Example: Enter the following test score matrix and
name it TESTS: 64 80 97 88
79 53 67 75
93 88 90 93
55 64 70 77
Press to start the MatrixWriter. Its menu
lets you choose how wide each column is (via KIS0
and [IER) and how the cursor moves after each
entry (either across, with [EVER; down, with [ETEEE;
or nowhere, with and IE['ES0).*** For this ex-
ample, set5TD notation, leave the column width as is,
and enter data by row (i.e. use [H1EXD):
JENTER)(9) JENTER](8 8JENTER), then (¥] (this estab-
lishes the column count in the matrix; from now on, the
machine will know when to begin a new row, so you
can finish data entry uninterrupted);
(ENTER] 7JENTER] JENTER] 3JENTER), etc. An ex-
tra exits the MatrixWriter and puts your com-
pleted matrix onto the stack—just as if you had keyed
itinthere. Now nameit: (" o] o] T E)S)(TIS)ENTER|STO).
*Note that the nature of your result (symbolic vs. numeric) will depend
onthe states of Flags -2 and -3. See page 78 for more about those flags.
**A vector is also a kind of array—though it has its own syntax, [ 1;
depending on the circumstances, it can be treated by the machine as
being either a row matrix or column matrix.
“**And the 2nd page of the menu has tools to add/extract rows/columns.
26 THe HP 48G/GX Pocker GuipeE