How do I exact all the indexes with a certain value?

I wrote a loop that scan through the channel that contains all the trigger markers and I set those with intensity >3 to 1, else =0. Now I have this variable (marker) that contains the trigger markers at the intensity of 1. I would like to get the indexes of marker with an intensity of 1. How should I do that? Thanks,

marker = zeros(size(Inpt_RZ2_chn002.dat));
for mi = 1:length(Inpt_RZ2_chn002.dat)-1
    if Inpt_RZ2_chn002.dat(mi) > 3
        marker(mi) = 1;
    else
        marker(mi) = 0;
    end
end
plot(marker)

Answer 1

[Matt J]

Don't use a loop. Just do,

marker = Inpt_RZ2_chn002.dat > 3;

The logical vector marker already functions as an index vector, e.g.,

greaterThanThree = Inpt_RZ2_chn002.dat(marker)

[ET]

Thanks, Matt

How do I get the indexes of all the ones into a new variable with only all the indexes of ones? I tried dsearchn which only gave me the first index.

[Matt J]

How do I get the indexes of all the ones into a new variable with only all the indexes of ones.

Why are the indices in logical form not enough?

x=(1:5)*10

x = 1×5

10 20 30 40 50

marker=(x>30)

marker = 1×5 logical array
   0   0   0   1   1

x(marker)

ans = 1×2

40 50

If you really do need numeric indices, use find()

find(marker)

ans = 1×2

4 5

[ET]

Why are the indices in logical form not enough?

I use the indices to epoch eeg data. Thanks Matt