bug#16706: emacs 24.3.1; calc/A command

bug#16706: emacs 24.3.1; calc/A command

[Bart Nielsen]

calc - single variable statistics tells me:

   Another commonly used mean, the RMS (root-mean-square), can be
computed for a vector of numbers simply by using the `A' command.


So:

I believe the RMS value for the vector [21 23 25 25] is 23.5584379788.  (RMS means ‘the root, of the mean, of the square — so 

<ret>
vM*
uM
Q

(returns that value)


A returns
47.1168759576


q1:  How do I figure out what A is doing?

q2: Isn’t this wrong?

Thanks

=====
Here’s the standard form for an error report: (the above just seemed cleaner. Maybe not.)
23.5584379788  

his bug report will be sent to the Bug-GNU-Emacs mailing list
and the GNU bug tracker at debbugs.gnu.org.  Please check that
the From: line contains a valid email address.  After a delay of up
to one day, you should receive an acknowledgment at that address.

Please write in English if possible, as the Emacs maintainers
usually do not have translators for other languages.

Please describe exactly what actions triggered the bug, and
the precise symptoms of the bug.  If you can, give a recipe
starting from `emacs -Q':

M-x calc
'[ 21 23 25 25 ]
<ret>
vM*
uM
Q

'[21 23 25 25 ]
A

leaves
2:  23.5584379788
1:  47.1168759576

on the stack.  Shouldn't A return 23.5584379788?




If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
For information about debugging Emacs, please read the file
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In GNU Emacs 24.3.1 (x86_64-apple-darwin13.0.0)
 of 2014-01-24 on bmac.home
Configured using:
 `configure '--prefix=/usr/local/Cellar/emacs/24.3' '--without-dbus'
 '--enable-locallisppath=/usr/local/share/emacs/site-lisp'
 '--infodir=/usr/local/Cellar/emacs/24.3/share/info/emacs'
 '--without-gnutls' '--without-x' 'CC=clang''

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Info

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  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
" H SPC DEL DEL DEL DEL DEL DEL SPC - SPC C a l c SPC
V e c t o r SPC M e d i a n " C-e C-@ - - - SPC s o
r t SPC DEL , SPC a v e r g DEL a g e SPC t h e SPC
m i d d l e DEL DEL DEL l DEL d l e C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-p C-@ - SPC a r i t h m e t i
c SPC m e a n ESC O A ESC O A ESC O A ESC O A ESC O
A ESC O A ESC O A C-x o ESC x c a l c RET ' 2 1 * 2
1 SPC + SPC 2 3 * 2 3 SPC + SPC 2 5 * 2 5 * 2 C-a (
s DEL DEL s q r t ( ( C-e ) / 4 ) RET C-y A C-h a C-g
C-h k A C-x o C-x o a A DEL C-x o C-x o SPC - - - SPC
n o , SPC i t ' DEL SPC o u g h t SPC t o SPC b e SPC
2 3 . 5 5 8 4 C-x o C-x o C-x o C-h C-g ' Y DEL C-y
C-a C-d C-d C-d C-d C-e RET RET v M * u + S U C-h k
S C-g C-x o C-x o ' s q r t ( C-g 4 / L 2 / E C-x o
C-x o C-x o C-x o C-s A ESC x r e p o r t SPC e m a
c s SPC b SPC RET

Recent messages:
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Mark saved where search started

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bug#16706: emacs 24.3.1; calc/A command

[Achim Gratz]

Bart Nielsen writes:
> A returns
> 47.1168759576
>
>
> q1:  How do I figure out what A is doing?

The result indicates that it returns the vector magnitude or absolute of
the vector, which is exactly twice the RMS value for a four-element
vector.  In other words, you'd need to divide by sqrt(n) after A.
Looking up "A" through the index leads to a correct description of what
it does.


Regards,
Achim.
-- 
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bug#16706: emacs 24.3.1; calc/A command

[Jay Belanger]

Hi Bart,

> calc - single variable statistics tells me:
>
>    Another commonly used mean, the RMS (root-mean-square), can be
> computed for a vector of numbers simply by using the `A' command.
>
>
> So:
>
> I believe the RMS value for the vector [21 23 25 25] is 23.5584379788.
> (RMS means ‘the root, of the mean, of the square — so

Of course, rms means "Richard M Stallman", too!

But as you noted, the manual is wrong.  I'm really surprised that such
an error has been around so long.  "A" should stand for "absolute
value", which for a vector should be the norm.
Offhand, I don't see the RMS function in Calc.  If it isn't there, I'll
(for now) remove that paragraph from the manual, and after the Emacs
feature freeze is over I'll put in the RMS function.  Then I'll put the
paragraph back in the manual, with the correct keybinding.

Jay

bug#16706: emacs 24.3.1; calc/A command

[Mattias Engdegård]

This bug seems to have been resolved but not closed, so let's do that.
A root mean square function (u R) has been present since 2015.