I should also mention that my verb(s) work for subarrays other than 2x2. e.g. if T is a 12x12 array T =: 12 12 $ 0 _2 12 100 2 4.5 1 7 _5.5 3.2 120 2 _100 3 5 18 4 is =: 12 $ 1 0 0 IsMax =: (is;is) ($$((>./=])@:,))&.>@:< interval T NB. max of 3x3 subarrays 12 12 $ , > |:"2 <"1 > IsMax
Also creates the correct array. -------------------------------------------- On Wed, 3/29/17, 'Jon Hough' via Programming <[email protected]> wrote: Subject: [Jprogramming] Unboxing after subarray function To: "Programming Forum" <[email protected]> Date: Wednesday, March 29, 2017, 4:38 PM I have a NxN matrix. For each 2x2 subarray of this (keep it simple, N is even), I want to calculate the maximum value and if the value of that cell equals the maximum of the 2x2 subarray write 1, else write 0. e.g. NB. T arbitrary 10x10 matrix T =: 10 10 $ 0 _2 12 100 2 4.5 1 7 _5.5 3.2 120 2 _100 3 5 18 4 interval =: ;.1 is =: 10 $ 1 0 IsMax =: (is;is) ($$((>./=])@:,))&.>@:< interval T So IsMax shows which elements are the max values of the 4x4 subarrays. Now I want to unbox and keep the indices correct. This appears to work 10 10 $ , > |:"2 <"1 > IsMax But is incredibly messy. I'm hoping there is a nicer/ more terse / elegant way to do this. Thanks, Jon ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
