Piece-wise linspace

Hi

I need to generate a vector (0's and 1's), when I'm given indices for the starting and endpoints of the 1's trains.

Example: m=zeros(1,10); starts=[1 5 9]; ends=[3 6 9];

the generated vector should be [1 1 1 0 1 1 0 0 1 0]

Any way of avoiding a loop? [starts(:):ends(:)] only looks at the first entry of the source vectors...

thanks Tozé

Answer 1

[Jan]

Do the sections overlap? If not, try this:

m         = zeros(1, 10);
starts    = [1 5 9];
ends      = [3 6 9];
m(starts) = 1;
m(ends)   = -1;
m         = cumsum(m);

If they sections are overlapping:

m         = zeros(1, 10);
p         = zeros(1, 10); 
starts    = [1 5 9];
ends      = [3 6 9];
m(starts) = 1;
m(ends)   = -1;
m         = cumsum(m);
p(m > 0)  = 1;

I cannot test this currently, so please keep care.

And perhaps this helps: FEX: interval merging.

Answer 2

[Bjorn Gustavsson]

Why bother searching for a cunning loop-free version (non-explicit) when the looped version is so straightforward? How much time does it take to come up with something clever compared to the potential gain in run-time?

HTH,

Answer 3

[Toze]

Hi HTH I have aprox. 10^10 elements in each run... Tozé

Answer 4

[Toze]

Hi Jan

With one minor change (m(ends) should be m(ends+1)), this is exactly what I was looking for .. a clever solution.