Nice :)
On Sat, Sep 7, 2019 at 2:00 AM Alex Harsanyi <alexharsa...@gmail.com> wrote:
> In fact, I updated the data frame package to be able to read the CSV file
> directly, without having to process it, so the example now becomes:
>
> #lang racket
> (require data-frame)
>
> (define df (df-read/csv "worldcities.csv" #:quoted-numbers? #t))
>
> (define ((is-city? name) v)
> (equal? (vector-ref v 0) name))
>
> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>
> ;; Produces:
>
> ;; '#(#("Perth" "Australia" -31.955 115.84)
> ;; #("Perth" "United Kingdom" 56.4003 -3.47))
>
> Alex.
>
>
> On Saturday, September 7, 2019 at 8:13:28 AM UTC+8, Alex Harsanyi wrote:
>>
>>
>> That database is simple enough to use directly, not sure if it needs a
>> separate package:
>>
>> #lang racket
>> (require data-frame)
>>
>> ;; The worldcities.csv file has all values quoted, so df-read/csv reads
>> them
>> ;; all as strings. Convert a series to numbers.
>> (define (->numeric df series)
>> (df-add-derived df series (list series) (lambda (v) (string->number (car
>> v)))))
>>
>> (define df (df-read/csv "worldcities.csv"))
>>
>> ;; Convert numeric series to numbers
>> (for ([series '("lat" "lng" "population")])
>> (->numeric df series))
>>
>> (define ((is-city? name) v)
>> (equal? (vector-ref v 0) name))
>>
>> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>>
>> ;; The above call produces:
>>
>> ;; '#(#("Perth" "Australia" -31.955 115.84)
>> ;; #("Perth" "United Kingdom" 56.4003 -3.47))
>>
>>
>>
>> Alex.
>>
>> On Friday, September 6, 2019 at 8:37:59 PM UTC+8, Laurent wrote:
>>>
>>> There's a small free database here too:
>>> https://simplemaps.com/data/world-cities
>>>
>>> I started writing a simple query system for it this morning (csv->rktd,
>>> then just list of assoc operations).
>>>
>>> On Fri, Sep 6, 2019 at 1:35 PM Sage Gerard <sa...@sagegerard.com> wrote:
>>>
>>>> Would geonames help?
>>>> http://www.geonames.org/
>>>>
>>>>
>>>> -------- Original Message --------
>>>> On Sep 6, 2019, 8:28 AM, Hendrik Boom < hen...@topoi.pooq.com> wrote:
>>>>
>>>>
>>>> On Thu, Sep 05, 2019 at 10:42:01PM -0700, Alex Harsanyi wrote:
>>>> ...
>>>> >
>>>> > >
>>>> > > A package containing a database of the positions of the major
>>>> cities and
>>>> > > countries would be nice too :)
>>>> > >
>>>> >
>>>> >
>>>> > A general facility able to resolve location names to GPS coordinates
>>>> would
>>>> > be a lot of work, and I don't have time for such a thing. Sorry.
>>>>
>>>> There must be a GPS database of cities available somewhere already.
>>>>
>>>> -- hendrik
>>>>
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