You'll want the more general form of indexing, using boxes.
i.3 4
0 1 2 3
4 5 6 7
8 9 10 11
(<1 1) { i.3 4
5
_ (<1 1)} i.3 4
0 1 2 3
4 _ 6 7
8 9 10 11
A more complete description of selection is here:
http://www.jsoftware.com/help/jforc/more_verbs_for_boxes.htm#_Toc191734399
Marshall
On Tue, Feb 28, 2012 at 11:49 PM, PackRat <pack...@anet.com> wrote:
> I have a table "b" (example below) which is the transpose of table "a"
> which is read in from a file. Here's what table b looks like, just so
> you have an idea of what's where:
>
> +--------+-----------+--------+--------+-----------+...
> |F |CAT |DE |CSX |XOM |...
> +--------+-----------+--------+--------+-----------+...
> |Ford |Caterpillar|Deere |CSX |Exxon Mobil|...
> +--------+-----------+--------+--------+-----------+...
> |3710 |665 |410 |890 |4000 |...
> +--------+-----------+--------+--------+-----------+...
> |19560307|19291202 |19330609|19801103|19991201 |...
> +--------+-----------+--------+--------+-----------+...
> |0 |0 |0 |0 |0 |...
> +--------+-----------+--------+--------+-----------+...
> |0 |0 |0 |0 |0 |...
> +--------+-----------+--------+--------+-----------+...
>
> The problem I'm having is with amending individual cells in both row 4
> and row 5 (the last two rows) of table b. (I've run into this problem
> before, but I created lengthy workarounds which are not really J-ish.
> I decided this time to ask the wisdom of the J community to finally
> find out once and for all what the "right" way of doing this kind of
> thing is.)
>
> I don't run into problems READING an individual cell, such as:
>
> stocksym=. toupper > (j { 0 { b)
>
> However, when I attempt to WRITE an amend into the jth (e.g., first)
> cell of row 4 of table b, for example:
>
> b=. (< stocknum) j } (4 { b)
>
> table b is incorrectly changed (compared to my intent, that is) from
> the table shown above to a list instead:
>
> +-+-+-+-+-+...
> |6|0|0|0|0|...
> +-+-+-+-+-+...
>
> Is there some "standard" way of making such amends within a table that
> I seem to be missing somewhere along the line? Thanks for your help!
>
>
> Harvey
>
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>
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