How is the performance of Position[] ..

*To*: mathgroup at smc.vnet.net*Subject*: [mg7041] How is the performance of Position[] ..*From*: cmchung at se.cuhk.edu.hk (Chung Cheong Ming)*Date*: Sat, 3 May 1997 22:04:37 -0400 (EDT)*Organization*: Engineering Faculty CUHK*Sender*: owner-wri-mathgroup at wolfram.com

I've got a problem, see anyone can shed some light. I have an array (a list of sublists) with the following structure, ARRAY = { { {a11a,a11b}, a12, ...}, { {a21a,a21b}, a22, ...}, { {a31a,a31b}, a32, ...}, : : { {am1a,am2b}, am2, ...}} |<----- n elements ----->| Thus I have a m by n matrix with the first element in each sublist as a 2-element list. My question is if I know a particular pair of this first element eg. {1000,2000}, how will be the computation of Position[] if I want to use this as a key to extract the row number where {1000,2000} situates in ARRAY. If anyone know of any formal literature (maybe Mathematica technical report), I would be very appreciated. Thanks Joseph