Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.



Re: correct syntax for matlab..
Posted:
May 14, 2013 3:32 AM


dpb <none@non.net> wrote in message <kmo69j$7nn$1@speranza.aioe.org>... > On 5/12/2013 1:38 AM, virat rehani wrote: > > counter=1; > > eligible=[10,2]; > > for i=1:M > > for j=1:M > > if (dis2(i,j)==1) > row=i; > > col=j; > > eligible(counter,1)=row; > > eligible(counter,2)=col; > > counter=counter+1; > > end > > end > > end > > I'm not so sure you did find what you're actually looking for altho you > haven't said clearly what the expected output is...let's look at what > you have > > counter=1; > eligible=[10,2]; % this isn't what you want it to be I'm sure... > > eligible here will simply be the vector 10,2 and will be overwritten the > first pass thru the following loop that satisfies the if > > Probably what you were looking for is > > eligible=zeros(10,2); > > But the question is why 10? > > for i=1:M % what's M??? > > Since the loops are running over the array dis2, on can assume > size(dis2)=[10,10] or larger or the loop would have failed on an address > out of bounds error. If so, then there are up to 100 possible results > from the if() tests if the content were full of 1's and the above > attempt at allocation would be way short. Only if you know there can be > no more than a total of 10 1's present would the allocation above be > sufficient. > > for j=1:M > if (dis2(i,j)==1) > eligible(counter,1)=i; > eligible(counter,2)=j; > counter=counter+1; > end > end > end > > The above will increment the counter and store the location of the i,j > indices in the next row of the eligible array and have length equal to > the number of 1's found in dis2. > > That's precisely what > > [eligible(:,1) eligible(:,2)]=find(dis2==1); > > will do. The only difference is that your loops traverse the array in > row order where as find operates in column order. If you need the > specific order then > > eligible=sortrows(eligible); > > Only difference between this posting/solution is that in previous I > assumed the array was either 0/1 so didn't use the '==1' in the argument > of FIND; if that's the case it is superfluous but if the data could be > something nonzero but not 1 then it is needed. > > And, of course, the ordering of the resultant vector wasn't considered > significant before. > > Here's at the command line example... > > >> x=rand(5); > >> x(x>.6)=1;x(x<1)=0; % make up a set of data > >> x > x = > 0 1 1 1 0 > 0 0 0 1 0 > 1 0 0 0 0 > 1 0 0 1 1 > 0 1 1 1 0 > Your solution... > >> k=1;for i=1:5,for j=1:5,if x(i,j)==1,e(k,:)=[i j];k=k+1;end,end,end > > The "Matlab way"...(or one of the ways, anyway)... > >> [e1(:,1) e1(:,2)]=find(x==1); > >> e1=sortrows(e1); > > >> all(all(e==e1)) > ans = > 1 > >> > > Shows oneforone consonance of each element in e and e1... > >  Dear sir I did it this way counter=1; eligible=[10,2]; for i=1:M for j=1:M if (dis2(i,j)==1) row=i; col=j; eligible(counter,1)=row; eligible(counter,2)=col; counter=counter+1; end end end



