GROUPFIND

Find groups of data from a vector.

Description

Extract groups of data from a vector. For example:

x=[0 1 2 2 1 0 -1 1 3 5 3];
groupfind(x>0)
ans =

     2 5
     8 11

In this case, the first group is from indices 2 to 5 and the second is from indices 8 to 11.

• MATLAB release: MATLAB 6.1 (R12.1)

[John McQueen]

Your program is truly amazing! It is the ultimate solution to everything I was looking for. I was astonished at how easy it is to use! Not only do you provide specific knowledge, but you also provide the MOTIVATION that has driven me to such success. This opportunity has surely changed my life. If you are skeptical like how I was, you will see the light!

[Piyush Singh]

Trivial bug in the code

>> x = [0 0 0 0 0 0 0]

x =

     0 0 0 0 0 0 0

>> groupfind(x>0)
??? Subscript indices must either be real positive integers or logicals.

Error in ==> groupfind at 47
ind(:,2)=temp([idx; end]); % create 2nd column first to allocate all memory

[Wladimir Alonso]

This function was very useful when I needed to plot only certain "fragments" of a time-series using the "plot" function:

blocks_of_relevant_points = groupfind(boolean_relevant_points>0);
for i=1:size(blocks_of_relevant_points,1)
    i_relevant_points_this_block = blocks_of_relevant_points(i,1):blocks_of_relevant_points(i,2);
    hold on
    plot(time_points(i_relevant_points_this_block), time_series(i_relevant_points_this_block));
end

In this way I managed to get rid of the lines that were connecting each fragment.

many thanks Mickey!