Re: Field coordinates and moving averages

[Michael Brand <michael.ch.brand@gmail.com>]

Hi Ben

On Tue, Nov 15, 2011 at 16:21, Benjamin Beckwith <bnbeckwith@gmail.com> wrote:
> #+TBLFM: $2=if(@# >=7, vmean(@-5$1..@0$1),string(""));

The above does not work because the range expression "@-5$1..@0$1" is
an Org construct and has to be evaluated for every affected row
already in Org, before it is given to Calc. It has therefore no other
choice than failing together with "$2 =" (out of range), the
expression "@# >= 7" is evaluated only in Calc later. This is one of
the reasons for which I added "field coordinates in formulas" (@# and
$#) in 2010-03.

There are at least two solutions with a Calc formula for this use
case:


1) range formula

The clean solution, already given by Nick:

On Tue, Nov 15, 2011 at 16:52, Nick Dokos <nicholas.dokos@hp.com> wrote:
> Try a range on the LHS:
> #+TBLFM: @7$2..@>$2=vmean(@-5$1..@0$1)


2) Calc subvec with field coordinates in formulas

This was the only solution before Carsten introduced range formulas in
2011-03 and might be interesting for understanding purposes:

| Daily Data | Moving Average |
|------------+----------------|
|         10 |                |
|         11 |                |
|         12 |                |
|         13 |                |
|         14 |                |
|         14 |         12.333 |
|         16 |         13.333 |
#+TBLFM: $2 = if(@# >= 7, vmean(subvec(@I$1..@>$1, @# - 6, @#)) +.0,
string("")); f-3

See also "Dynamic variation of ranges" in "field coordinates in
formulas (@# and $#)" here:
http://orgmode.org/worg/org-hacks.html
reachable about one or two pages down with the current section
numbering here:
http://orgmode.org/worg/org-hacks.html#sec-1-3-5
For such a two-dimensional moving range, Calc subsrc/subvec is still
the simpler solution to get the triangle than several range formulas
would be.

If you change the input field 16 to 20 you see that "+.0" is required
in the formula to get 14.000 instead of 14 for the result. See "Which
float format shows the fraction part also when the latter is zero?"
here:
http://orgmode.org/worg/org-faq.html#table-float-fraction

Michael