Joe,
If you are working with color space manipulations, you might also
want to look at the image3 addon (available from Jsoftware) and
various image scripts on my J pages
http://ww2.lafayette.edu/~reiterc/j/index.html
one of which is
http://ww2.lafayette.edu/~reiterc/j/withj/color_space.html
Best,
Cliff
Joseph Peralta wrote:
Yes, that's very helpful. Thanks for clarifying this for me.
Joe
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Dan Bron
Sent: Wednesday, June 07, 2006 2:02 PM
To: Programming forum
Subject: Re: [Jprogramming] Matrix x Vector List
Joe,
When you have a dyadic verb (one which takes both a left and a right
argument), and you want to apply that verb to different size pieces
("cells") of the arguments, use the rank conjunction " .
In your case, you want to pair the rows of the left argument with the table
of the right argument. Rows have one dimension, and so are rank 1 ,
tables have two dimensions, and so are rank 2 . Consequently, you want to
do:
short_data =: }:"1 data
short_data x"1 2 yuvmat
which results in an N by 3 table, where N is #data . I, personally,
would write:
short_data x"_1 _ yuvmat
which means "pair the /items/ of the left argument with the /entire/ of the
right argument.". The items of short_data happen to be rows, and the
entire of yuvmat happens to be a table. The results are unchanged.
Essentially, what " does is pair up the requested parts ("cells") of the
two arguments, then applies the verb between them. That is, for each item
(row) in short_data, it takes a copy of the entire (table) yuvmat, and
matrix-multiplies the two. You can experiment with other cells:
show_pairings =: ,&:<
short_data show_pairings"1 2 yuvmat
short_data show_pairings"_1 _ yuvmat
short_data show_pairings"0 2 yuvmat
short_data show_pairings"1 0 yuvmat
Hope this helps,
-Dan
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--
Clifford A. Reiter
Mathematics Department, Lafayette College
Easton, PA 18042 USA, 610-330-5277
http://www.lafayette.edu/~reiterc
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