Re: Finding the Position of Elements in a List that Contain

*To*: mathgroup at smc.vnet.net*Subject*: [mg102219] Re: [mg102157] Finding the Position of Elements in a List that Contain*From*: Gregory Lypny <gregory.lypny at videotron.ca>*Date*: Sat, 1 Aug 2009 04:03:25 -0400 (EDT)*References*: <200907310953.FAA19267@smc.vnet.net>

Just what I needed. Thank you, Leonid, and I will thumb through your book. One of the things I want to work on is a function that finds a word (string that is space delimited on both sides or one side if occurring at the beginning or end of a string). It would work something like If theSearchString is among the words of theTargetString then return True This is a function that Runtime Revolution (a.k.a MetaCard and originally HyperCard) has, and it is indispensible. Regards, Gregory On Fri, Jul 31, 2009, at 7:12 AM, Leonid Shifrin wrote: > Hi Gregory. > > Position[listOfStrings,x_/;StringMatchQ[x, __ ~~ searchString ~~ > ___]], > > if your list is not too large. If it is, and you want to speed it > up, one quick > solution is to use StringCases (as you did) to produce the list of > matches, > and then the <memberPositions> function that I developed in my book: > > http://www.mathprogramming-intro.org/book/node596.html > > ,see at the bottom of the page - you feed both the original list and > the list of results to it, like this: > > memberPositions[listOfStrings, > StringCases[listOfStrings, __ ~~ searchString ~~ ___]] > > I expect this to be fast even for large lists of strings: > StringCases is much faster when used on a whole list of strings > rather than used separately on each string, and my function is also > rather fast. I did not benchmark you problem though, so it is just > my guess that this way will be faster than the first one above. > > > Hope this helps. > > Regards, > Leonid > > > > > On Fri, Jul 31, 2009 at 1:53 PM, Gregory Lypny <gregory.lypny at videotron.ca > > wrote: > Hello everyone, > > Suppose I have a list of strings, say, sentences such as > > listOfStrings = {"The cat is here.", "It's not here.", "Not > in the > catalogue,", "Where is the cat?"} > > and a string I want to search for > > searchString = "cat" > > I can use StringCases to pick off the elements that contain the search > string > > StringCases[listOfStrings, __ ~~ searchString ~~ ___] > > {{"The cat is here."}, {}, {"Not in the catalogue,"}, {"Where > is the > cat?"}} > > But what if I just want to know the positions of the elements that are > hits? In this case, it's > > {1, 3, 4} > > If I use > > Position[listOfStrings, ___ ~~ theString ~~ ___] > > I get > > {} > > which is not what I expect. Also how can I have my searchString > treated like it is a word so that 3 is not one of the hits? > > Any hints would be much appreciated. > > Gregory > >