Finding the index of a particular point

Hello all,

I am working with a curve having 1000 points along horizontal axis. Lets say that the value is zero along the curve up to 300th point and then it starts to increase smoothly and saturates to +1 at 700th point. Beyond that the curve remains unchanged at +1 till the end. The min and max value of the curve do not change, but the points from which they start to vary change when i run a loop;

start:

     n(1:300) = 0; n(701:end) = 1;

first iteration:

     n(1:255) = 0; n(706:end) = 1;

Second iteration:

     n(1:250) = 0; n(711:end) = 1;

and so on;

I need to know the indices to these two points at which the changes start in each iteration. Can anyone please help me how i should write the codes to ge this?

Thanks Sazzad

Answer 1

[Azzi Abdelmalek]

You can use

diff(n)

%Or

n=[0 0 0 0 0 0 0 0 0.5 0.6 .7 .8 .9 1 1 1 1 1 1 1 1]
idx1=find(n==0);
idx1=idx1(end)   % first point
idx2=find(n==1,1)% second point

Answer 2

[Andrei Bobrov]

s = n == 0 | n == 1;
s = s(:)';
out = [strfind(s,[1 0 ]), strfind(s,[0 1])+1];

[SAZZAD HOSSAIN]

Thanks Andrei. Works perfect