This line looks suspicious:
(define results (make-vector years (make-vector (vector-length
fecundity) 0)))
The "(make-vector (vector-length fecundity) 0)" expression will create a
single vector, than it creates the outer vector will all elements pointing
to it. It is not a matrix, but a "column" vector where each element is
referencing the same row vector. This means that if you update an element
in one of the rows, the same value will "appear" in all other rows. The
only row that is different is the first one which you initialize in the
line:
(vector-set! results 0 (make-vector (vector-length fecundity) 10))
What you probably want is a vector of vectors, which can be built like this
(define results (for/vector ([index (in-range years)]) (make-vector
(vector-length fecundity) 0)))
Alex.
On Sunday, February 10, 2019 at 3:40:42 PM UTC+8, travis.h...@gmail.com
wrote:
>
> Hi All,
>
> I'm an R programmer that has recently started learning Racket. I decided
> to start by trying to create a simple age-structured population model. In
> R, I would initialize a matrix and use nested for loops to move through the
> elements of the matrix and propagate the population forward through time.
> For my first attempt in Racket (
> https://gist.github.com/hinkelman/3ee6115cdd7f0a4c8f1672b7d8df5c27), I
> used for* to loop through a vector of vectors. The code in that gist
> doesn't quite work. There is apparently something wrong with how I'm using
> vector-set! such that "rows" in my vector of vectors are being updated
> prematurely. I would greatly appreciate it if someone could point out what
> I'm doing wrong there. I'm also interested in suggestions for alternative
> approaches because it seems unlikely that I have written this code in
> idiomatic Racket.
>
> Thanks,
>
> Travis
>
> P.S. If it is helpful, here is a gist (
> https://gist.github.com/hinkelman/d5b8414b0c6383057d7846509a724bbf) with
> the R code that I was trying to write in Racket.
>
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