Getting used to Calc's Radian convention

Getting used to Calc's Radian convention

[H. Dieter Wilhelm]

Hello (:-),

Calc's unit convention of revolution per minute (rpm) is derived from
the angular speed and not from a frequency.  One does not need to type
the factor of `2 pi' when calculating, for example, the circumferential
velocity from the radius and some value in rpm.  So far so good.

But it has the slight aesthetic drawback that now the velocity turns out
to be in units of radians.

n <- 1 rpm
r <- 1 m
n r -> 2 pi rad m / min

Since Radian is a base unit I can only get rid of it when dividing by
`rad'.  But I think a Radian is not a real physical unit and wouldn't it
be consistent, when evaluating, to assign just the value of 1 to it?

What are your thoughts?

     Dieter
-- 
best wishes
H. Dieter Wilhelm
Darmstadt, Germany

Re: Getting used to Calc's Radian convention

[Emanuel Berg]

dieter@duenenhof-wilhelm.de (H. Dieter Wilhelm) writes:

> Calc's unit convention of revolution per minute (rpm)
> is derived from the angular speed and not from a
> frequency. One does not need to type the factor of `2
> pi' when calculating, for example, the
> circumferential velocity from the radius and some
> value in rpm. So far so good.
>
> But it has the slight aesthetic drawback that now the
> velocity turns out to be in units of radians.
>
> n <- 1 rpm
> r <- 1 m
> n r -> 2 pi rad m / min
>
> Since Radian is a base unit I can only get rid of it
> when dividing by `rad'. But I think a Radian is not a
> real physical unit and wouldn't it be consistent,
> when evaluating, to assign just the value of 1 to it?
>
> What are your thoughts?

My thoughts are: What?!

What are you doing, and what are you using? (Are you
even using Emacs?)

There are two macros:

    degrees-to-radians
    radians-to-degrees

But this is simple enough for you to rewrite into
functions if you prefer that.

First thought though, why can't you just get any unit
you like by simple arithmetics?

-- 
underground experts united

Re: Getting used to Calc's Radian convention

[jay.p.belanger]

> > Calc's unit convention of revolution per minute (rpm)
> 
> > is derived from the angular speed and not from a
> 
> > frequency. One does not need to type the factor of `2
> 
> > pi' when calculating, for example, the
> 
> > circumferential velocity from the radius and some
> 
> > value in rpm. So far so good.
> 
> >
> 
> > But it has the slight aesthetic drawback that now the
> 
> > velocity turns out to be in units of radians.
> 
> >
> 
> > n <- 1 rpm
> 
> > r <- 1 m
> 
> > n r -> 2 pi rad m / min


> My thoughts are: What?!

He's referring to Calc (part of Emacs), which can work with units (such as meters, radians, etc.)

Calc doesn't "know" that the rad probably shouldn't be there; perhaps there could be a simple way of telling it.

Re: Getting used to Calc's Radian convention

[Emanuel Berg]

jay.p.belanger@gmail.com writes:

> He's referring to Calc (part of Emacs), which can
> work with units (such as meters, radians, etc.)
>
> Calc doesn't "know" that the rad probably shouldn't
> be there; perhaps there could be a simple way of
> telling it.

Perhaps the shell tool 'units' can be used? That's what
I always use to deal with the strange units from the
UK, and the USA.

-- 
underground experts united

Re: Getting used to Calc's Radian convention

[H. Dieter Wilhelm]

Emanuel Berg <embe8573@student.uu.se> writes:

> jay.p.belanger@gmail.com writes:
>
>> He's referring to Calc (part of Emacs), which can
>> work with units (such as meters, radians, etc.)
>>
>> Calc doesn't "know" that the rad probably shouldn't
>> be there; perhaps there could be a simple way of
>> telling it.
>
> Perhaps the shell tool 'units' can be used? That's what
> I always use to deal with the strange units from the
> UK, and the USA.

Yes somebody else suggested `units' to me and it seems also very
powerful, but I prefer to stay in Emacs, Calc really is a killer feature
for engineers!

Bye
        Dieter

-- 
Best wishes
H. Dieter Wilhelm
Darmstadt, Germany

Re: Getting used to Calc's Radian convention

[H. Dieter Wilhelm]

jay.p.belanger@gmail.com writes:

>> > Calc's unit convention of revolution per minute (rpm)
>> 
>> > is derived from the angular speed and not from a
>> 
>> > frequency. One does not need to type the factor of `2
>> 
>> > pi' when calculating, for example, the
>> 
>> > circumferential velocity from the radius and some
>> 
>> > value in rpm. So far so good.
>> 
>> >
>> 
>> > But it has the slight aesthetic drawback that now the
>> 
>> > velocity turns out to be in units of radians.
>> 
>> >
>> 
>> > n <- 1 rpm
>> 
>> > r <- 1 m
>> 
>> > n r -> 2 pi rad m / min
>
>
>> My thoughts are: What?!
>
> He's referring to Calc (part of Emacs), which can work with units
> (such as meters, radians, etc.)

Sorry, I made myself not clear and it is basically a question about
physics but there seems to be not separate Calc mailing list.

> Calc doesn't "know" that the rad probably shouldn't be there; perhaps
> there could be a simple way of telling it.

As I said I'm happy with the angular notion of Calc's rpm unit but
it. Maybe it would help to "degrade" Radian -- it is in Calc a base unit
-- to a constant like pi and when converting to base units it simply
vanishes when saying `u b' calc-base-units or an additional unit
function for converting it to its numerical value?

Have fun with Calc
-- 
Best wishes
H. Dieter Wilhelm
Darmstadt, Germany