Re: Re: Counting Runs

*To*: mathgroup at smc.vnet.net*Subject*: [mg51998] Re: [mg51934] Re: [mg51890] Counting Runs*From*: DrBob <drbob at bigfoot.com>*Date*: Sat, 6 Nov 2004 02:08:59 -0500 (EST)*References*: <200411040650.BAA18131@smc.vnet.net> <200411050717.CAA06890@smc.vnet.net> <opsg0lmi1fiz9bcq@monster.cox-internet.com> <opsg0pe8woiz9bcq@monster.cox-internet.com> <D9733954-2F93-11D9-85F1-000A95ED10EE@yale.edu>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

And the new winner -- for both speed and simplicity -- is: brt4[v_List] := Frequencies@Split[v][[All, 1]] It returns each pair in opposite order to the other methods, but that's not a significant drawback, I don't think. Bobby On Fri, 5 Nov 2004 20:33:23 -0500, János <janos.lobb at yale.edu> wrote: > It must be machine or OS dependent. > > I re-discovered Hanlon3 method :) and ran it with Bobby's newest. I > don't have Bobby's data so I generated random didgits in the 0-9 range > > Here are the results: > > In[28]:= > v = Table[Random[Integer, > {0, 9}], {i, 1, 10^7}]; > > In[29]:= > Timing[({First[#1], > Length[#1]} & ) /@ > Split[Sort[First /@ > Split[v]]]] > Out[29]= > {35.58*Second, {{0, 898901}, > {1, 899397}, {2, 901191}, > {3, 899449}, {4, 900824}, > {5, 900262}, {6, 899338}, > {7, 900293}, {8, 900196}, > {9, 901311}}} > > In[32]:= > Timing[({First[#1], > Length[#1]} & ) /@ > Split[Sort[Split[v][[All, > 1]]]]] > Out[32]= > {38.67999999999998*Second, > {{0, 898901}, {1, 899397}, > {2, 901191}, {3, 899449}, > {4, 900824}, {5, 900262}, > {6, 899338}, {7, 900293}, > {8, 900196}, {9, 901311}}} > > My machine is a 1.25Ghz G4 with 2G Ram and with OSX 10.3.5. > > János > On Nov 5, 2004, at 7:38 PM, DrBob wrote: > >> I found an even faster (rather obvious) solution: >> >> hanlonTreat[v_] := {First@#, Length@#} & /@ Split@Sort[Split[v][[All, >> 1]]] >> >> It about 80% faster than hanlon4. >> >> Bobby >> >> On Fri, 05 Nov 2004 17:16:56 -0600, DrBob <drbob at bigfoot.com> wrote: >> >>> I timed the posted methods except Andrzej's -- it's the only one that >>> works only for +1/-1 data -- plus a couple of my own that I haven't >>> posted. David Park's method seems the same as the fastest method, >>> hanlon3. I modified all methods to return a pair {x, number of runs >>> in x} for each x in the data. >>> >>> Two of Bob Hanlon's methods beat all the rest of us -- but one of his >>> is the slowest method, too. >>> >>> I've posted a notebook at the Run Counts link at: >>> >>> http://eclecticdreams.net/DrBob/mathematica.htm >>> >>> Bobby >>> >>> On Fri, 5 Nov 2004 02:17:54 -0500 (EST), Selwyn Hollis >>> <sh2.7183 at misspelled.erthlink.net> wrote: >>> >>>> Hi Greg, >>>> >>>> The following seems to work pretty well: >>>> >>>> runscount[lst_?VectorQ] := >>>> Module[{elems, flips, counts}, >>>> elems = Union[lst]; >>>> flips = Cases[Partition[lst, 2, 1], {x_, y_} /; x =!= y]; >>>> counts = {#, Count[Most[flips], {#, _}]} & /@ elems; >>>> {x1, x2} = Last[flips]; >>>> counts /. {{x1, y_} -> {x1, y+1}, {x2, y_} -> {x2, y+1}}] >>>> >>>> Example: >>>> >>>> Table[Random[Integer, {1, 5}], {20}] >>>> runscount[%] >>>> >>>> {2, 2, 3, 1, 3, 2, 2, 3, 1, 1, 2, 3, 1, 1, 3, 1, 1, 2, 2, 2} >>>> >>>> {{1, 4}, {2, 4}, {3, 5}} >>>> >>>> >>>> ----- >>>> Selwyn Hollis >>>> http://www.appliedsymbols.com >>>> (edit reply-to to reply) >>>> >>>> >>>> On Nov 4, 2004, at 1:50 AM, Gregory Lypny wrote: >>>> >>>>> Looking for an elegant way to count runs to numbers in a series. >>>>> Suppose I have a list of ones and negative ones such as >>>>> v={1,1,1,-1,1,1,1,1,1,-1,-1,-1,-1,1}. >>>>> I'd like to create a function that counts the number of runs of 1s >>>>> and >>>>> -1s, which in this case is 3 and 2. >>>>> >>>>> Greg >>>>> >>>>> >>>> >>>> >>>> >>>> >>> >>> >>> >> >> >> >> -- >> DrBob at bigfoot.com >> www.eclecticdreams.net >> >> > > ------------------------------------------------------------------- > János Löbb > Yale University School of Medicine > Department of Pathology > Phone: 203-737-5204 > Fax: 203-785-7303 > E-mail: janos.lobb at yale.edu > > > > -- DrBob at bigfoot.com www.eclecticdreams.net

**References**:**Counting Runs***From:*Gregory Lypny <gregory.lypny@videotron.ca>

**Re: Counting Runs***From:*Selwyn Hollis <sh2.7183@misspelled.erthlink.net>