Re: How do I test for existence of a list element?

*To*: mathgroup at smc.vnet.net*Subject*: [mg112717] Re: How do I test for existence of a list element?*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Tue, 28 Sep 2010 06:04:09 -0400 (EDT)

On 9/27/10 at 5:48 AM, andre.robin3 at wanadoo.fr (andre.robin3) wrote: >I recently had the same problem, but for a more general case : How >to test the existence of a deeply embedded element in a ragged >structure ? >Say that the position of the element is specified by : list={i,j,k >..} >my solution was something like : >existenceTestQ[exp_, list_] := Module[{res}, >res = False; >ReplacePart[exp, list :> (res = True)]; >res >] >may be not elegant, but sufficient =46irst generate a small ragged array In[5]:= ragged = MapThread[ Take[#1, #2] &, {RandomInteger[{0, 100}, {5, 10}], RandomInteger[{1, 10}, 5]}] Out[5]= {{58,15,40,35,61,97,62,21,64,23},{44,68},{39,49},{43,62,99,10,51,= 4},{1,6,83,6,11,93,89,67}} And now test for something known to be present: In[6]:= Length /@ {Position[ragged, 1, Infinity], Cases[ragged, {___, 1, ___}], Cases[ragged, 1, Infinity]} Out[6]= {1,1,1} And finally test for something known not to be present In[7]:= Length /@ {Position[ragged, 0, Infinity], Cases[ragged, {___, 0, ___}], Cases[ragged, 0, Infinity]} Out[7]= {0,0,0} That is either Cases or Position can be used to determine the presence/absence of something in a ragged array.