Package descriptive, working with frequency lists

This is just a code improvement (??) suggestion. If I get that rightly, I
would do it the following way. Given a list with values v, and a list f
with the corresponding frequencies i calculate the inner product v . f
which is equivalent to v^T f and then divide by the sum apply("+", f), for
your example

v:[178, 179, 180, 181, 182]$
f:[2, 4, 5, 6, 3]$
m: v . f;
3604
t: apply("+",f);
20
m / t, numer;
180.2

So i suggest you write your function so that it takes the two lists s, c in
order to avoid the for loop and shorten your code

frequ_mean(v, f) := block([],
v . f / apply("+", f)
)$

Best regards,
/Fotis


On Tue, Dec 11, 2012 at 12:36 PM, Andreas Goebel <a-goebel at gmx.de> wrote:

> Hi,
>
> this is my first post here, so hello from me. I?m a math teacher at a
> grammar school in germany.
>
> My students have to work with frequency lists, like this:
>
> Size 178 179 180 181 182
> count 2 4 5 5 3
>
> While the package "descriptive" provides functions for computing mean,
> standard deviation and so on for lists, it does not do so for frequency
> lists. So my students would have to enter the list like this:
> 178 178 179 179 179 179 ....
>
> which is not really an option.
>
> To solve this, I have tried a bit with the descriptive package and have
> introduced a function frequ_mean like this:
>
> /* UNIVARIATE DESCRIPTIVE STATISTICS */
>
> /* Arithmetic mean for frequency list */
> frequ_mean(x) := block([i,mean, total],
> mean:0, total:0,
> for i:1 thru length(x) do( block(
> mean:mean+x[i][1]*x[i][2],
> total:total+x[i][2]
> ) ),
> mean/total
> )$
> /* Arithmetic mean */
> ....
>
> A test run:
> /* [wxMaxima: input start ] */
> l:[[178,2],[179,4],[180,5],[181,5],[182,3]];
> /* [wxMaxima: input end ] */
> /* [wxMaxima: input start ] */
> load(descriptive);
> /* [wxMaxima: input end ] */
> /* [wxMaxima: input start ] */
> frequ_mean(l);
> /* [wxMaxima: input end ] */
> /* [wxMaxima: input start ] */
> float(%);
> /* [wxMaxima: input end ] */
>
> gives a correct result.
>
>
> So my questions are:
> - does this make sense?
> - should there be some checks to avoid errors, for instance if the list
> has the wrong form?
> - who maintains the descriptive package? Whould he / she like to
> implement functions for frequency lists himself, or should I do that and
> submit them (and if so, how?)?
> - I would also need to draw histograms for data like that, but have no
> idea at the moment how to achieve this
>
> Best regards,
>
> Andreas
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