Did you happen to notice David's use of the word "pages" at the end of his message? It makes a great visual image to explain the array.
I was wondering if it has been used in this context before, or does it have a long and checkered APL or J history? Linda -----Original Message----- From: programming-boun...@forums.jsoftware.com [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of David Ward Lambert Sent: Wednesday, September 05, 2012 9:57 PM To: programming Subject: Re: [Jprogramming] duplicate row of matrix Right! "Matrix multiplication" usually means something else. You want a sort of element-by-corresponding-element multiplication. B ; A +-------+-------+ |1 1 0 0|1 1 1 1| |0 0 1 1|1 1 2 2| | |1 1 3 3| | |1 1 4 4| +-------+-------+ A solution uses rank conjunction twice. I couldn't begin to understand it the first time I saw this sort of construction. Then one day I wrote rank rank and retrospectively realized what I'd written and understood. I practiced rank with sentences like 'abc' "2 i. 2 3 4 My thoughts to construct this sentence: First I realized that you need to multiply row by row. The ("1) adverb ensures this. The frames of these two matrices disagree because there are 2 rows in B and 4 in A. The next adverb ("_ 1) means (because ultimately the final verb is dyadic) "use all of the left array with each row of the right hand array". B * ("1) ("_ 1) A 1 1 0 0 0 0 1 1 1 1 0 0 0 0 2 2 1 1 0 0 0 0 3 3 1 1 0 0 0 0 4 4 Finally, inserting append between the pages gives ,/B*"1"_ 1 A 1 1 0 0 0 0 1 1 1 1 0 0 0 0 2 2 1 1 0 0 0 0 3 3 1 1 0 0 0 0 4 4 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
