HP 34S: Find an element in a matrix? - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: Not HP Calculators (/forum-7.html) +--- Forum: Not quite HP Calculators - but related (/forum-8.html) +--- Thread: HP 34S: Find an element in a matrix? (/thread-1375.html) HP 34S: Find an element in a matrix? - Gerald H - 05-22-2014 05:36 AM Can someone please explain the syntax/function of MFD? I need to find a given matrix element to implement Shanks square form factorization method. RE: HP 34S: Find an element in a matrix? - Thomas Klemm - 05-22-2014 06:10 AM From the code I'd say: ( y mat -> r ) Where mat is a matrix descriptor and y is the element you search. Cheers Thomas Code: ```/* Find a specified element in a matrix  */             LBL'MFD'             ABS             M-ALL             x[<->] Y m_find_loop::       x=?[->]Y             JMP m_found             ISG Y             JMP m_find_loop m_found::       DROP             RTN``` RE: HP 34S: Find an element in a matrix? - Gerald H - 05-22-2014 06:51 AM To post #2: Thank you. I don't understand r. For 5,6,7,8 stored in registers 20 to 23 stack y: 55 x: 20.0401 returns 24.02301 and stack y: 7 x: 20.0401 returns 22.02301 Presumably the second result indicates "found"? How should this result be interpreted? RE: HP 34S: Find an element in a matrix? - Thomas Klemm - 05-22-2014 07:10 AM You probably want the index of the element. The matrix descriptor is still in the last x register. Therefore you can use: Code: ```RCL L M.IJ``` For 7 you get (x, y) = (3, 1). For 55 you get an Error: Out of range. RE: HP 34S: Find an element in a matrix? - Gerald H - 05-22-2014 07:33 AM To post #4: Thank you & yes that is the info I needed. Will now get to work on Shanks SQFF.