On Tuesday, October 18, 2016 at 5:48:07 PM UTC+2, David K. Storrs wrote:
> Hi Pierre,
>
> Does matrix-map-cols do what you want? It's the last function on page
> https://docs.racket-lang.org/math/matrix_poly.html
>
> Also, welcome to Racket!
>
> Dave
>
>
>
>
> On Mon, Oct 17, 2016 at 7:00 PM, Pierre-Henry Frohring
> <frohring.p...@gmail.com> wrote:
> Hello,
>
>
>
> First time here, and just a few hours into Racket...
>
> It is not going to be rocket science ;-).
>
>
>
>
>
> Context:
>
>
>
> I am using Emacs and org-mode to map each heading of an org file to a html
> file.
>
> Result: one org file → one static website.
>
> https://github.com/phfrohring/org-to-blog
>
>
>
> The org file contains data that is exported to a tsv file:
>
> https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#data
>
>
>
> A code block in the org file is evaluated:
>
>
> https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#processing
>
>
>
> And produces a stacked-chart from the tsv data:
>
> https://github.com/phfrohring/org-to-blog/blob/master/test/blog.org#result
>
>
>
>
>
> The tsv data is parsed into a kind of matrix `M` where each cell `M[i][j]` is
> a
>
> string.
>
> ex: `M[i][0]` is the column "day" i.e. contains dates
>
> `M[i][1]` is the column "description" i.e. contains strings
>
>
>
> In order to use operations over "day" column (adding dates, ...) it is needed
> to
>
> parse that column with something like: `iso8601->date` but not the
> "description"
>
> column.
>
>
>
> So, it is needed to apply a vector of functions `vF = [f_0,f_1,...]` to `M =
>
> [col_0,col_1,...]` such that: `(matrix-apply vF M) = M'` where:
>
>
>
> M' = [f_0(col_0),f_1(col_1),...,f_n(col_n)]
>
>
>
> Well, this function `matrix-apply` does not seem to exist and my attempt at
>
> implementing it feels clunky to say the least (ex: fs is not a vector):
>
>
>
> (define (matrix-apply fs m)
>
> (cond [(= (length fs) (matrix-num-cols m))
>
> (matrix-augment
>
> (map (λ (f_col)
>
> (apply
>
> (λ (mat) (matrix-map (car f_col) mat))
>
> (cdr f_col)))
>
> (zip
>
> fs
>
> (matrix-cols m2))))]
>
> [#t (error fs)]))
>
>
>
> (define m2 (matrix [[1 2 3 4]
>
> [1 2 3 4]]))
>
>
>
> (matrix-apply (list sqr sqr sqr sqr) m2)
>
>
>
> => (array #[#[1 4 9 16] #[1 4 9 16]])
>
>
>
>
>
> Am I missing the elephant in the corridor? Is an implementation floating
>
> somewhere?
>
>
>
> Thx!
>
>
>
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Thx Dave!
Assuming I understood the doc correctly:
(matrix-map-cols f M) → (Matrix B)
f : ((Matrix A) -> (Matrix B))
M : (Matrix A)
So, `f` expects a matrix as an input. What I am trying to do is to apply a
vector of functions `[f_i]` such that each `f_i` acts on a vector: the columns
of the matrix M. Also, the type M[i,j] may differ from one column to the other.
Something that would look like:
(matrix-map-cols [f] M) → (Matrix [B_1 B_2 … B_n])
where each f_i in [f] has type: f_i : (List A_i) → (List B_i)
M : (Matrix [A_1 A_2 … A_n])
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