select can also eliminate items
(<<<0 1 5){i.7 3
6 7 8
9 10 11
12 13 14
18 19 20
On Tue, May 19, 2020, 7:27 PM HH PackRat <[email protected]> wrote:
> Feel free to skip this apologetic preface that applies to all questions I
> ask:
>
> By way of excuse, I'm 74, and my memory has been failing little by
> little over the last number of years. I looked at some J code I had
> written 8-12 years ago and was astounded at what I used to be able to
> do--nothing major, mind you, but yet good, decent code! I've been
> sort of a lifetime "beginner" since 2006 (maybe reaching "advanced
> beginner", if there is such a thing!), doing programming on and off as
> I have need (which also doesn't help the memory). However, comparing
> what I wrote years ago with what I struggle with now is showing that
> my memory of what certain J primitives and combinations do is slipping
> with time. (Years ago I wrote my own beginner-level task-organized
> vocabulary of the kinds of things I typically need to do in my
> particular programming interests, and I heavily depend upon that until
> I run into something where the issue is not addressed in my
> compilation.) So, please bear with me when I ask questions with
> simple answers that you may think everybody should already know. I've
> been a hobbyist programmer since 1975, mostly with versions of BASIC.
> (I started with a MITS Altair PC and Microsoft's original BASIC. A
> good number of years ago I asked Bill Gates to autograph my manual for
> that BASIC since he wrote the code.) But times have changed, and now
> I simply LOVE working with the J language because it fits my needs so
> well in developing relatively simple programs (without writing all
> those loops!), especially for dealing with data and such in my stock
> market (and other) interests. I have no need to make my code tight,
> fast, or short, as perhaps most of you need to do in your work--for
> me, it just has to work correctly!
>
> After all that, finally, my QUESTION:
>
> J has all sorts of ways of creating, assembling, disassembling,
> selecting, changing, and finding data in atoms, lists, and tables.
> However, in no index of any of my books or ebooks about J, nor in the
> (old) Vocabulary, nor in NuVoc have I been able to find how to DELETE
> tables or any of their rows.
>
> For example, here is the cleaned up (of double quotation marks)
> beginning of unusually-formatted data from a particular data source
> that I'm trying to reformat according to standard:
>
> +---------|-----------|--
> |May 08|May 07|
> +---------|-----------|--
> | 2020 | 2020 |
> +---------|-----------|--
> | 664.35| 652.35|
> +---------|-----------|--
> | 660.21| 653.00|
> +---------|-----------|--
> | 664.56| 657.12|
> +----------|----------|--
> | 657.67| 651.29|
> +----------|-----------|--
> | - | - |
> +----------|-----------|--
> | 1.84% | 1.19% |
> +----------|-----------|--
>
> I need to delete rows 0, 1, and 7--how to do that? (that is, leaving
> a new table of rows, formerly 2 to 6, now 0 to 4)
>
> One thought I had was maybe to use some sort of boolean mask
> expression using either 00111110 or its opposite 11000001. But, even
> using that in some way, I still don't know how to physically get rid
> of those rows, so that they don't exist any more. This question and
> its answer is probably a "piece of cake" for most of you, but, right
> now, the answer is not obvious to me. (After seeing one or more
> answers, I'll probably say to myself, "Of course! I should have known
> that!")
>
> By the way, just FYI, the first two deleted rows will be replaced with
> the row that was created in the question in my previous message, but
> that replacement is not what this question is dealing with--I'm rather
> sure I can deal with that without help at this point. After that,
> it's just a matter of moving one of the price rows to a different
> position, converting the hyphens to zeros, and chronologically
> reversing the data. I've never moved and inserted a row before, but I
> think I'll be able to figure that one out. (If not, you know I'll be
> back.) ;-)
>
> Again, thanks in advance for your help with this!
>
> Harvey
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
