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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: MATA all combinations / pairs of a row |

Date |
Fri, 7 Oct 2011 23:37:34 +0100 |

I'd check out books on combinatorial algorithms. Nick On Fri, Oct 7, 2011 at 11:28 PM, Sebastian Eppner <eppner@uni-potsdam.de> wrote: > Hi, > yes, based on the select and rowsum = 2 logic I wrote this > (unfortunately it has to use one loop... first I thought that may be > ok... in reality in really is time consuming... if there are ANY ideas > out there how to prevent the loop, i' be very grateful). > > > > BASIC = ( 1,1,1) \ (1,1,0) \ (1,0,1) \ (0,1,1) \ (0,0,1) \ (0,1,0) \ (1,0,0) > PROPERTIES = (0,9,10) \ (0.45, 0.2, 0.35) > > > PROP1 = PROPERTIES[1,.] > PROP1 = diag(PROP1) > PROP1 = BASIC * PROP1 > > PROP2 = PROPERTIES[2,.] > PROP2 = diag(PROP2) > PROP2 = BASIC * PROP2 > > Now I have 3 Matrices with all the information i needed. The problem was now: > >> For each row/combination in BASIC I need to find all PAIRS of Ones >> that are contained in the combination. For any pair, I need to >> multiply: >> PROP1 of Element1 * PROP1 of Element2 * abs(PROP2 of Element1-PROP2 >> of ELEMENT2) > > I calculated the latter not only for pairs, but for all rows (later i > only use the pair rows) > > PAIRS = rowmax(PROP1):*rowmin(PROP1):*(rowmax(PROP2)-rowmin(PROP2)) > > Then I calculate the sum of all pairs contained in the first row. see > the select() which only selects those rows that are: > - contain only elements that are also elements in row one of BASICS > (that i do by subtracting all rows from the first one, and then I look > if there is a -1 somewhere) > - contain only pairs (as Nick suggested that means the rowsum is 2) > > mata: result = colsum(select(PAIRS, (rowmin(BASIC[1,.]:-BASIC):>-1):& > rowsum(BASIC):==2)) > > of course i need the result for all the other rows too! thats where i > cant think of anything but a loop (****jsdf) > > forvalues i=2/`lastrow' { > mata: result = result \ colsum(select(PAIRS, > (rowmin(BASIC[`i',.]:-BASIC):>-1):& rowsum(BASIC):==2)) > } > > any suggestion would be magic. > Thanks, > Sebastian > > On Thu, Oct 6, 2011 at 2:16 AM, Nick Cox <njcoxstata@gmail.com> wrote: >> One idea only from me. Look at -select()- and think of rowsums being 2. >> >> Nick >> >> On Wed, Oct 5, 2011 at 10:08 PM, Sebastian Eppner <eppner@uni-potsdam.de> wrote: >>> Hi, >>> I have N elements. In this example N will be 3. But in my application >>> it will be usually around 7, going up to 20 in some cases… >>> >>> Each element can be either 1 or 0. My basic matrix has all 2^N, here >>> 2^3 permutations of the elements: >>> >>> BASIC = ( 1,1,1) \ (1,1,0) \ (1,0,1) \ (0,1,1) \ (0,0,1) \ (0,1,0) \ >>> (1,0,0) \(0,0,0) >>> >>> The elements have 2 “properties” , PROP1 and PROP2 each, stored in 2 >>> rows of another matrix, for example: >>> >>> PROPERTIES = (1.4,4.6,8.1) \ (0.2, 0.4, 0.4) >>> >>> Every row in BASIC resembles a unique combination of the elements. >>> What I want to do, is to calculate some indicators for every >>> combination, using the Properties of the elements. >>> >>> An easy example would be to calculate the total sum of PROP1 for each >>> combination. I just need to multiply the “diagonalized” first row of >>> the PROPERTIES Matrix with the BASIC Matrix and then calculate the >>> rowsum of this resulting matrix. >>> >>> >>> What I want to do now is more complex and I am really stuck. The >>> indicator I want to calculate now is the following: >>> >>> For each row/combination in BASIC I need to find all PAIRS of Ones >>> that are contained in the combination. For any pair, I need to >>> multiply: >>> >>> PROP1 of Element1 * PROP1 of Element2 * abs(PROP2 of Element1-PROP2 >>> of ELEMENT2) >>> >>> It is the sum of all PAIRS that I need to know for every row…. >>> >>> >>> Of course, not every row has PAIRS in it… all rows with only 1 One >>> have no pairs, so the result for these rows should be 0 (or missing, I >>> don’t care). >>> >>> Also, many rows (those with only 2 Ones) have only a single Pair… >>> >>> In my Example with 3 elements, only the first row sums up more than >>> one (3) Pair(s)…. >>> >>> >>> I am looking for a way to solve this problem by not using loops… and >>> as much matrix algorithms as possible. Since I have a lot of BASIC >>> Matrices with more elements than 3… I guess the whole thing would be >>> very very time consuming if I started smth with loops… Maybe there is >>> no way to get rid of any loop… any idea would be very welcome (even >>> some, with a little looping). >> * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: MATA all combinations / pairs of a row***From:*Sebastian Eppner <eppner@uni-potsdam.de>

**Re: st: MATA all combinations / pairs of a row***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: MATA all combinations / pairs of a row***From:*Sebastian Eppner <eppner@uni-potsdam.de>

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