"Joe User" joeu2004 wrote:
When I want a repeatable sequence of random numbers
I generate a range using RAND() and then copy-paste
values to freeze the results.
Yeah, I 'spose I could make that work for my purposes.
Actually not. I was wondering why I didn't think of that rather obvious
approach. When I remembered why, I also realized that even disabling the
initial seeding (presumably based on "system time") would not satisfy my
needs.
I was able to learn some details about VB Rnd because it does produce a
repeatable sequence unless you call Randomize. But what I learned was made
possible only because the default seed is documented in KB 231847.
Since KB 828795 fails to document the default seed (I suspect now there is
none), it does not help to disable the initial seeding. I am still stuck
with trying to infer the 3 factors in the Wichman-Hill algorithm,
ass-u-me-ing that KB 828795 is correct. I had developed an inferential
algorithm in Dec'09. And for that, any RAND result will do; I do not even
need a sequence.
I was never entirely satisfied with the results of the inferential approach
because it was always off in some low-order binary bits. The difference was
small enough to be "close enough for government work", but too large to be
explained by some nuance of computer arithmetic.
I was hoping that I now had a new approach to try. But I am wrong.
----- original message -----
"Joe User" joeu2004 wrote in message
...
"Charles Williams" wrote:
http://support.microsoft.com/kb/828795 may help.
Y'don't 'spose that's the very same support.microsoft.com/kb/828795 that I
referred to in my posting? ;-) Y'had to read all the way down to the 4th
paragraph (6th sentence).
No, it does not help.
When I want a repeatable sequence of random numbers
I generate a range using RAND() and then copy-paste
values to freeze the results.
Yeah, I 'spose I could make that work for my purposes.
I am still interested in how to seed RAND or how it is seeded, if only to
satisfy my curiosity.
----- original message -----
"Charles Williams" wrote in message
...
I don't know of a way to seed the 2003 RAND function, or what the
algorithm is, but
http://support.microsoft.com/kb/828795
may help.
When I want a repeatable sequence of random numbers I generate a
range using RAND() and then copy-paste values to freeze the results.
Is there any way to seed (initialize) the Excel 2003 RAND function so
that
subsequent calls to RAND result in a repeatable sequence?
----- previous message -----
"Joe User" joeu2004 wrote in message
...
Is there any way to seed (initialize) the Excel 2003 RAND function so
that
subsequent calls to RAND result in a repeatable sequence?
I have tried seeding the VBA Rnd function, to no avail. No surprise that
the two are unrelated. It was a "hail Mary" try.
Although I know how to get a repeatable Rnd sequence, I do not want to
use
the VBA Rnd function for my purposes.
I could also easily implement my own PRNG, even using the
Wichman-Hill(1982)
algorithm described in support.microsoft.com/kb/828795. (Actually, I
already have.) But that, too, does not suit my purposes.
I want to use Excel RAND per se; no alternatives.
KB 44738 suggests that there might be a RANDOMIZE variable somewhere;
perhaps in an INI file, perhaps in the Registry now, or perhaps a command
line switch. But I have not (yet) succeeded in locating such a variable
for
Excel 2003.
I did try executing Excel in safemode, to no avail. Another
"hail Mary" try. I even tried the command line switch /randomize=0, to
no
avail. A "shot in the dark".
(KB 44738 refers to earlier versions of Excel in which RAND did produce a
repeatable sequence by default, and it required setting the RANDOMIZE
variable to change that.)
Alternatively, does anyone know exactly how the Excel 2003 RAND function
is
seeded?
Presumably by some manipulation of "system time"; but that is subject to
interpretation. I can speculate as well as anyone. I am looking for the
actual algorithm. KB 828795 does not explain that; and my Google
searches
have been fruitless (so far).