Is it possible to do calculations with GNU Octave using measuring units?

tubbadu@lemmy.kde.social to Open Source@lemmy.ml – 27 points –

Hello! In qalc I can do calculations using measuring units like this:

> 5 W * 3 s

  (5 watts) × (3 seconds) = 15 J

I'd like to be able to do something similar also in GNU Octave. I think the symbolic library could be a place to look at, but I found nothing "already done". Do any of you know of a way to achieve this functionality?

9

The Octave miscellaneous package has embedded GNU units as a function which should be helpful.

It looks interesting, but more focused on conversions than actual operations it seems:

octave:37> a.value = 100
a =

  scalar structure containing the fields:

    value = 100
    unit = W

octave:38> a.unit = 'W'
a =

  scalar structure containing the fields:

    value = 100
    unit = W

octave:39> b.value = 3
b =

  scalar structure containing the fields:

    value = 3
    unit = s

octave:40> b.unit = 's'
b =

  scalar structure containing the fields:

    value = 3
    unit = s

octave:41> a*b
error: binary operator '*' not implemented for 'scalar struct' by 'scalar struct' operations

I think I've found a solution. Matlab has implemented symunits in the symbolic toolbox and I've found the original? on Github. Hopefully it is compatible to GNU Octave.

This looks very VERY promising! I'll try to install it tomorrow and Post here the results! Thanks?

I downloaded it and tried to run it, but it gets stuck in a loop and I don't know how it could be fixed:

error: max_recursion_depth exceeded
error: called from
    baseUnitSystem

it seems the problem is in the line

coreUnits = buildCoreUnits(u.baseUnitSystem);

in the file u.m, I think because u.baseUnitSystem tries to "call itself". I don't know what this should be supposed to do, and have no idea on how to possibly fix it :(

I don't think symbolic will solve your problem at all

With symbolic variables J, s and W, the Ws won't be converted to J automatically.

automatically no, but perhaps there's a way to replace it. If there's a way to check if a variable is "divisible by another symbolic one" then it would be not so hard to implement this behavior