The page http://www.jsoftware.com/jwiki/JohnRandall/FourierTransformAndPolynomialMultiplication contains the definition rou=:[: r. 2p1 * i. % ] I'd like to supplement with the shorter definition rou=:_1^2%] but the page is write protected. Why? - Bo
--- Den tors 6/1/11 skrev Roger Hui <[email protected]>: > Fra: Roger Hui <[email protected]> > Emne: [Jprogramming] FFT > Til: "Programming forum" <[email protected]> > Dato: torsdag 6. januar 2011 07.54 > http://www.jsoftware.com/jwiki/Essays/FFT > > cube =: ($~ q:@#) :. , > roots =: +...@]^:(0>[) (_1^2%]) ^ i...@-: > floop =: 4 : 'for_r. i.#$x do. (y=.{."1 y) ] x=.(+/x) > ,&,:"r (-/x)*y end.' > fft =: (] floop&.cube 1&ro...@#) > f. :. ifft > > This is a rare practical use of a high rank array. > ("High" means greater than 4, say.) The only other > "use" that I know of is the complete tensor of order n. > http://www.jsoftware.com/help/dictionary/dccapdot.htm > > The expression ,&,:"r in floop can be simplified to > ,:"r > if r is nonzero. This suggested that perhaps the > definition > of atom0 ,: atom1 is incorrect. (Should have shape 2 > > instead of 2 1.) > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
