Re: Some function like Positionbut uses criteria, not pattern?

*To*: mathgroup at smc.vnet.net*Subject*: [mg99483] Re: Some function like Positionbut uses criteria, not pattern?*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Wed, 6 May 2009 05:28:03 -0400 (EDT)

On 5/5/09 at 5:37 AM, nma at 12000.org (Nasser Abbasi) wrote: >Position[] works by returning position of elements which matches a >pattern. This is all good and well. >But sometimes, I need to find the positions (i.e index) of elements >that matches a criteria, not a pattern. >For example, using pattern >a = {1, 0, 4, -5, 8} >Position[a, 0] >Out[15]= {{2}} >But what if I wanted the position of the elements which, say, are >larger than 3? this is not a pttern, but a criteria. Which in this >example should find elements which are in position 3 and 5 in list >'a' above. Here is one way to accomplish what you want In[5]:= Pick[Range[Length@a], a, _?(# > 3 &)] Out[5]= {3,5} Alternatively, you could use Position as follows: In[6]:= Position[a, _?(# > 3 &)] Out[6]= {{3,5}}