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## Re: org-tables with monetary amounts

 From: Derek Feichtinger Subject: Re: org-tables with monetary amounts Date: Tue, 13 Oct 2020 09:10:30 +0200 User-agent: mu4e 1.4.1; emacs 26.2

```Hi,

On Mon, Oct 12 2020, Eric S Fraga <e.fraga@ucl.ac.uk> wrote:

> On Monday, 12 Oct 2020 at 10:22, Christian Moe wrote:
>> I think I was thinking about adding mode flags for unit computations,
>> like in the imagined example above (`\$3=\$2+\$1;u'), similar to what has
>> been done for duration computations.
>
> This would be very useful, actually.  I use embedded calc all the time
> with units; being able to use some of the same expressions in a table
> would be highly welcome.

The functions that one can use in calc formulas can be extended using
the 'defmath' lisp command. I paste here from my notes (not about

+++++++++++++++++++++++++++++++
Defining a new calc function for unit conversion with defmath
#+BEGIN_SRC emacs-lisp
(defmath uconv (expr target-units &optional pure)
(math-convert-units expr target-units pure))
#+END_SRC

#+RESULTS:
: calcFunc-uconv

| km     | ft           |
|--------+--------------|
| 2.5 km | 8202.0997 ft |
#+TBLFM: \$2=uconv(\$1, ft)

Using the units from the table header (if the 3rd arg is given to
uconv, the output is stripped of the unit):

|  km |        ft |
|-----+-----------|
| 2.5 | 8202.0997 |
#+TBLFM: \$2 = uconv(\$1 * @<\$1, @<\$2, t)

The standard calc function usimplify also works for this use
case:

|  km |        ft |
|-----+-----------|
| 2.5 | 8202.0997 |
#+TBLFM: \$2 = usimplify(\$1 * @<\$1 / @<\$2)

A lisp equivalent of the above
#+begin_src elisp
(calc-eval "usimplify(2.5 km / ft)")
#+end_src

#+RESULTS:
: 8202.09973753

Let's define a function that converts to base units
#+begin_src elisp
(defmath ustd (expr) (math-simplify-units (math-to-standard-units expr nil)))
#+end_src

#+RESULTS:
: calcFunc-ustd

| distance | time   | speed       | std unit speed   | speed in ft/s    |
|----------+--------+-------------+------------------+------------------|
| 3 km     | 2.5 hr | 1.2 km / hr | 0.33333333 m / s | 1.0936133 ft / s |
#+TBLFM: @2\$3=\$1/\$2::@2\$4=ustd(\$3)::@2\$5=uconv(\$-1, ft/s)
++++++++++++++++++++++++++++++++++++

--
Paul Scherrer Institut
Dr. Derek Feichtinger                   Phone:   +41 56 310 47 33
Group Head HPC and Emerging Technologies  Email: derek.feichtinger@psi.ch
Building/Room No. OHSA/D17
Forschungsstrasse 111
CH-5232 Villigen PSI

```