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20040510: Question on ucar.units package: getting scale factor


Salam alaikum.

>Date: Mon, 10 May 2004 10:44:28 -0400
>From: "El-Badrawi,Rashad" <address@hidden>
>Organization: UCHC
>To: <address@hidden>
>Subject: Question on ucar.units package

The above message contained the following:

> I am trying to implement support for units in our software using your
> units package. It has proven very helpful, but I have the following
> question: I need to break the 'end unit' (e.g. micro-molar - micro
> moles per liter-) into its building blocks (i.e. moles and liter)
> with the correct scale and exponent for each. I have no problem in
> knowing the building blocks and the exponent of each by retrieving the
> 'factors'. However, I cannot find a way in which I can specifically
> retrieve that the scale of the 'mole' factor is 10-6, and the scale of
> the 'm3' factor is '1000'. The scaling seems to come back mixed.
> Is there a way of doing that? Thanks for your help.

I *think* I know what you're asking.

That the multiplicative factors are "mixed", as you say, is
unavoidable.  This is because an infinite number of unit specifications
can be equivalent:

    nanomoles per cubic centimeter
    micromoles per liter
    millimoles per cubic meter

I suggest that you use the factor from a canonical or standard unit
(e.g., "micromoles per liter) and divide it into the factor from the
unit in question in order to arrive at a canonical factor for the mole
part of the unit product.

Contact me if you'd like an example.

>       Regards,
>       Rashad
> Rashad Badrawi                                      Research Associate I
> Center For BioMedical Imaging                 address@hidden
> Department of Cell Biology                       (860) 679 - 3296

Steve Emmerson

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