matlab - finding indeces of similar group elements -

i have vector test2 includes nan 0 , 1 in random order (we cannot make assumption).

test2 = [nan 1 1 1 0 0 0 nan nan nan 0 0 0 1 1 1 0 1 1 1 ]; 

i group elements containing consecutive 1 , have in separte vectors start , finish first , last index of groups.

in case start , finish should be:

start = [2 14 18]; finish = [4 16 20]; 

i tried adapt code provided here coming solution not working...could me right solution , tell me why 1 tried doesn't work?

a = (test2 ==1); d = diff(a); start = find([a(1) d]==1);                        % start index of each group finish = find([d - a(end)]==-1);                  % last index of each group   start =       2    14    18   finish =       2     3     5     6     7     8     9    10    11    12    14    15    18    19 

i using matlab r2013b running on windows. tried using matlab r2013a running on ubuntu.

a = (test2 ==1) d=diff([0 0]) start=find(d==1) finish=find(d==-1)-1 

padding 0 @ beginning , end easiest possibility. special cases group starts @ index 1 or ends @ last index don't cause problems.

full output:

>> test2 = [nan 1 1 1 0 0 0 nan nan nan 0 0 0 1 1 1 0 1 1 1 ]  test2 =    columns 1 through 16     nan     1     1     1     0     0     0   nan   nan   nan     0     0     0     1     1     1    columns 17 through 20       0     1     1     1  >> = (test2 ==1)  =    columns 1 through 16       0     1     1     1     0     0     0     0     0     0     0     0     0     1     1     1    columns 17 through 20       0     1     1     1  >> d=diff([0 0])  d =    columns 1 through 16       0     1     0     0    -1     0     0     0     0     0     0     0     0     1     0     0    columns 17 through 21      -1     1     0     0    -1  >> start=find(d==1)  start =       2    14    18  >> finish=find(d==-1)-1  finish =       4    16    20  >>