{ is the primitive you want. Something like:
{ (<"1 ,/dates) ,&< (<"1 hours)
should get you started. Maybe
((}:$dates),(#hours),5) $ , ;@> { (<"1 ,/dates) ,&< (<"1 hours)
?
This works, although it uses boxes a lot. Another option which works for the
test case is valid if this is a true Cartesian product in years, months,
days, hours, and minutes:
> { 2010 2009 2010 ; 1 ; 1 2 3 4 ; 0 ; 15 30 45 60
, i.e. (list of years);(list of months);(list of days);(list of hours);(list
of minutes)
Marshall
-----Original Message-----
From: programming-boun...@jsoftware.com
[mailto:programming-boun...@jsoftware.com] On Behalf Of Bill Harris
Sent: Monday, December 27, 2010 5:07 PM
To: programming@jsoftware.com
Subject: [Jprogramming] Cartesian products
I've been working in R too long, and my J is rusty.
I'm trying to take what seems like the Cartesian product of two
arrays. In particular, I've got a list of lists of dates, and I want
to turn them into ISO timestamps with a consistent HMS appended to them.
The dates list might look like
dates =: 1 4 3 $ 2010 01 01 2010 01 02 2010 01 03 2010 01 04
dates =: dates, 4 3 $ 2009 01 01 2009 01 02 2009 01 03 2009 01 04
dates =: dates, 4 3 $ 2010 01 01 2010 01 02 2010 01 03 2010 01 04
That's 3 sets of data, each with 4 dates, and each date with 3
components. (In general, each set of data could have a different
number of dates.)
The complete hours list looks like
hoursmins=: 24 (<95 0) } 24 60 #: 15 * >: i. 96
but a simple version for this example might only have 4 times:
hours =: 4 2 $ 0 15 0 30 0 45 0 60
What I want looks roughly like
2010 01 01 00:15:00.00
2010 01 01 00:30:00.00
2010 01 01 00:45:00.00
2010 01 01 00:60:00.00
2010 01 02 00:00:00.00
.
.
.
2010 01 04 00:60:00.00
2009 01 01 00:15:00.00
.
.
.
The last step needs the isotimestamp verb from dates, so I need to get
to lines of the form
2010 01 01 0 15
2010 01 01 0 30
and so forth. The rank of that result should be 3 16 5: 3 sets of 16
date-time stamps, each with 5 components.
I've tried lots of alternatives, including variants on catalog and on
Henry's JfC ,"_1 _ "_ _1, all to no avail. I suspect it's trivial; can
someone help?
Thanks,
Bill
PS: I apologize if this comes through twice. I originally sent it from
the wrong email address, which I suspect will get it blocked.
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