dpb <firstname.lastname@example.org> wrote in message <email@example.com>... > On 3/5/2013 9:16 PM, Eric wrote: > > Hi, > > > > I know I should be able to figure this out based on previous posts, but > > I still cannot find the correct solution. Within matrix A (nx1 matrix), > > I want to find the first instance that a value BW is 10 units less than > > BW--I'll call this value DROP. It is not a min or max value. I am just > > trying to index points on a force waveform so I can eventually integrate > > the area between points. > > > > Specifically: > > BW= 650; DROP = BW-10; > > [event1,ind1] = A(DROP,1); > > > > Using this, I get an error 'Indexing cannot yield multiple results'. > > I tried using find but all the values will be positive numbers. > ... > > ix=find(A==DROP,1); % the first index > A(ix) % the value at that index > > NB: If A is floating point and not integer-value, the problem of exact > comparisons for floating point values may rear its head...the values > you've shown are integers well withing DP resolution so will be stored > exactly, but that's not necessarily so in general of course. > > -- Thanks for this. You were correct that the problem of exact comparisons for floating point values became an issue because all numbers in A were non-integers. I rounded the values using floor since I do not need to be accurate to a tenths decimal place with the data I am working with.