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Is it possible to do calculations with GNU Octave using measuring units? (lemmy.kde.social)

submitted 5 months ago by [email protected] to c/[email protected]

9 comments fedilink hide all child comments

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?

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[–] [email protected] 6 points 5 months ago* (last edited 5 months ago) (1 children)

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

[–] [email protected] 3 points 5 months ago (1 children)

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

[–] [email protected] 4 points 5 months ago (2 children)

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.

[–] [email protected] 4 points 5 months ago

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

[–] [email protected] 2 points 5 months ago (1 children)

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
    <unknown>

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 :(

[–] [email protected] 2 points 5 months ago

It seems that the implementation of classdev in Octave is unfortunately not complete enough yet.😒

[–] [email protected] 1 points 5 months ago (1 children)

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

[–] [email protected] 1 points 5 months ago (1 children)

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

[–] [email protected] 2 points 5 months ago

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