Matrix multiplication: Difference between revisions

Matrix multiplication (view source)

Revision as of 05:16, 2 September 2009

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→‎{{header|J}}: lang tags, use mp instead of x to prevent confusion with x used as argument later

Tikkanz

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Revision as of 17:44, 14 August 2009 (view source) rosettacode>Kevin Reid m (alphabetize TI-*) ← Older edit		Revision as of 05:16, 2 September 2009 (view source) Tikkanz (talk \| contribs) m (→‎{{header\|J}}: lang tags, use mp instead of x to prevent confusion with x used as argument later) Newer edit →
Line 609: =={{header\|J}}== Matrix multiply in J is just <ttcode>+/ .</ttcode>. For example: <lang j> xmp =: +/ . NB. Matrix product ▼ A =: ^/~>:i. 4 NB. Same A as in other examples (1 1 1 1, 2 4 8 16, 3 9 27 81,:4 16 64 256)▼ B =: %.A NB. Matrix inverse of A▼ '6.2' 8!:2 A x B▼ 1.00 0.00 0.00 0.00▼ 0.00 1.00 0.00 0.00▼ 0.00 0.00 1.00 0.00▼ 0.00 0.00 0.00 1.00▼ ▲ A =: ^/~>:i. 4 NB. Same A as in other examples (1 1 1 1, 2 4 8 16, 3 9 27 81,:4 16 64 256) ▲ B =: %.A NB. Matrix inverse of A ▲ ▲ '6.2' 8!:2 A xmp B ▲ 1.00 0.00 0.00 0.00 ▲ 0.00 1.00 0.00 0.00 ▲ 0.00 0.00 1.00 0.00 ▲ 0.00 0.00 0.00 1.00 </lang> The notation is for a generalized inner product so that <lang j> ~~x ~:/ .. y NB. boolean inner product (<tt>~: </tt>is "not equal" (exclusive or) and<tt> . </tt>is "and")~~ x .~:/ .= . y NB. ~~which~~boolean ~~rows~~inner ofproduct x(<tt>~: ~~are~~</tt>is ~~the~~"not ~~same~~equal" as(exclusive ~~vector~~or) y?and<tt> . </tt>is "and") x + ./ .= y NB. ~~number~~which rows of ~~places~~x ~~where~~are ~~each~~the ~~row of x~~same ~~equals~~as vector y? x + / .= y NB. number of places where each row of x equals vector y </lang> etc.