HP -11C Owner's Handbook Manual page 29

54 Section 3: Numeric Functions
Example
To Calculate
Keystrokes
Permutation
Example: 10 items in
arrangements of 3 at
atime. 10 [ENTER 10.0000
3HPix) 720.0000
Combination
Example: 10 items in
sets of 3 at atime. 10 (ENTER 10.0000
7 3(e)[en.x) 120.0000
Statistics Functions
Random Number Generator
The HP-11C's random number generator uses either an auto-
matically stored seed (zero), or a seed you key in, to initiate a
uniformly distributed pseudo-random number sequence in the
range 0 <r < 1.* Because of Continuous Memory, the sequence will
continue until a new initial seed is stored.
Random Number Seed. To initiate a new random number
sequence at any time, place a new seed in the random number
generator by keying in any number 0 <n <1' and pressing (STO)[f)
(RAN#]. To generate a random number, simply press [f] (RAN#]. The
new random number will appear in the displayed X-register. ([f)
RAN | affects the stack in the same way as recalling a number from
a storage register.) The newly generated random number also
becomes the seed for the next random number in the current
sequence. Whenever Continuous Memory is reset, or when a power
failure occurs, the random number seed is set to zero. (Repeated use
of the same value for a random number seed will produce
repetitions of the same random number sequence.)
* Passes the spectral test (Knuth, Vol. 2).
+f a number whose magnitude is > 1 is used as a seed, the decimal point in the stored
version af the number will be shifted to the left of the firet significant digit. For example,
123.0, 12.3, and 0.123 would all be stored as 0.123 by [STO)(F)[RAN®
~~ vw
—
~~ yw
Section 3: Numeric Functions 55
Random Number Example Display
Generation Keystrokes
To store 0.5764 asa
random number seed:
(Arbitary Seed) (5764 0.5764 «|
STO|lf
Seed stored RAN# 0.5764 |
To generate a random
number series based on
the above seed: (RANA 0.3422
(A(RANS 0.2809
For a further discussion of the random number generator, refer to
page 217, Random Numbers, in part III of this handbook.
Accumulating Statistics
(£4) is a two-number function that calculates statistics of the
values in the X- and Y-registers. The results are automatically
accumulated in storage registers Ry through Rs.
T>
z>
Y>
x>
Any values remaining in Ro through Rs from previous
calculations or storage operations will be included in
subsequent statistics accumulations. To ensure that all
accumulations registers are set to zero before beginning a
new series of accumulations, press [f] CLEAR (clears Ro
through Rs and the stack) before beginning the operation.
L