R help - Dec 2007 - unit attribute to list elements

Hi,

I've started my own (first) package, part of which consists in  
listing common physical constants (Planck's constant, the speed of  
light in vacuum, etc). I'm wondering what would be a good way of  
dealing with pairs of value/unit.

> constants <- list( cel = 2.99792458e8 , #m/s
> Z0 = 376.730313461, #ohm
> eps0 = 8.854187817e-12,#F/m
> mu0 = 4*pi*1e-7,#N/A^2
> G = 6.67428e-11 # m^3 kg-1 s-2
> )

I thought I could include the unit in the names attribute of each  
element, as in :
> names(constants$cel)<- " speed of light in vacuum [m.s^-1]"

Writing this for every element is very redundant... Is there any way  
to access and set the name of each first level element of the list?
> namesFirstLevelElements(constants)<- c(" speed of light in vacuum  
> [m.s^-1]",
> "impedance of vacuum [some unit]",
> ...)

Quite possibly, I'm completely on the wring track;

- maybe such a package already exists

- a custom class or structure would be more appropriate? I don't  
really know how to deal with classes, though, and I'd like to keep  
the access to the constants' values as direct and generic as possible.

Many thanks in advance,

baptiste

_____________________________

Baptiste Augui?

Physics Department
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag
http://projects.ex.ac.uk/atto

Is this what you want?
> Lines <- "cel 3.0 m/s
+ Z0 367 ohm
+ eps0 8.9e-12 F/m
+ "
> Constants.DF <- read.table(textConnection(Lines), as.is = TRUE)
> Constants <- as.list(Constants.DF[[2]])
> names(Constants) <- Constants.DF[[1]]
> for(i in seq_along(Constants)) comment(Constants[[i]]) <-
Constants.DF[i, 3]
>
> # get value
> Constants$Z0
[1] 367
> # get comment
> comment(Constants$Z0)
[1] "ohm"
> # add another Constant
> Constants$e <- 2.7
> comment(Constants$e) <- "exp"

On Dec 28, 2007 2:33 PM, baptiste Augui? <ba208 at exeter.ac.uk>
wrote:
> Hi,
>
> I've started my own (first) package, part of which consists in
> listing common physical constants (Planck's constant, the speed of
> light in vacuum, etc). I'm wondering what would be a good way of
> dealing with pairs of value/unit.
>
>
> > constants <- list( cel = 2.99792458e8 , #m/s
> > Z0 = 376.730313461, #ohm
> > eps0 = 8.854187817e-12,#F/m
> > mu0 = 4*pi*1e-7,#N/A^2
> > G = 6.67428e-11 # m^3 kg-1 s-2
> > )
>
>
> I thought I could include the unit in the names attribute of each
> element, as in :
>
> > names(constants$cel)<- " speed of light in vacuum
[m.s^-1]"
>
>
> Writing this for every element is very redundant... Is there any way
> to access and set the name of each first level element of the list?
>
> > namesFirstLevelElements(constants)<- c(" speed of light in
vacuum
> > [m.s^-1]",
> > "impedance of vacuum [some unit]",
> > ...)
>
>
> Quite possibly, I'm completely on the wring track;
>
> - maybe such a package already exists
>
> - a custom class or structure would be more appropriate? I don't
> really know how to deal with classes, though, and I'd like to keep
> the access to the constants' values as direct and generic as possible.
>
> Many thanks in advance,
>
> baptiste
>
> _____________________________
>
> Baptiste Augui?
>
> Physics Department
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> Phone: +44 1392 264187
>
> http://newton.ex.ac.uk/research/emag
> http://projects.ex.ac.uk/atto
>
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