Extract multiple matrix from a vector

Hello to all,

Say you have a vector containing zones with consecutive values of zero and zones with numbers other than zero, like in the example:

v = [1 2 3 5 5 0 0 0 0 1 4 2 0 0 5 8 0 0 1 5 8 5 0 0 0]

Nevertheless, imagine that in the actual vector I have the non zero and zero zones vary in length from a couple of hundred to a couple pf thousand points.

I need to extract from my vector the non zero zones and place them into a cell array (say for example zones{} because the non zero zones have different lengths) and so far the my efforts did not output a good result (I tried manipulating the index with "find(v == 0)"). Has anybody encountered this challenge?

Best regards, Jean

Answer 1

[Andrei Bobrov]

v = [1 2 3 5 5 0 0 0 0 1 4 2 0 0 5 8 0 0 1 5 8 5 0 0 0];
v1 = v~=0;
out = arrayfun(@(x,y)v(x:y),strfind([0 v1],[0 1]),strfind([v1 0] ,[1 0]),'un',0);

[Fangjun Jiang]

+1. That is better. I can't seem to remember this method although I've seen it several times.

[Andrei Bobrov]

Hi Fangjun! This idea belongs to Matt Fig (use strfind for this targets).

Answer 2

[Fangjun Jiang]

v = [0 1 12 3 5 55 0 0 0 0 1 4 22 0 0 5 8 0 0 1 5 85 5 0 0 0 12 0];
s=num2str(v);
c=regexp(s,'0\s|\s0','split');
d=cellfun(@str2num,c,'uni',false);
e=cellfun('isempty',d);
f=d(~e);
celldisp(f)

f{1} =
     1    12     3     5    55
f{2} =
     1     4    22
f{3} =
     5     8
f{4} =
     1     5    85     5
f{5} =
    12

[Jean]

Hello,

Thank you very much for your answer. However, can you tell me how to get the indexes of these values (it will be useful in my algorithm)?

[Fangjun Jiang]

Use the following code to get the starting position of each non-zero zone.

%%

v = [0 1 12 3 5 55 0 0 0 0 1 4 22 0 0 5 8 0 0 1 5 85 5 0 0 0 12 0];

NonZeroFlag=v~=0;

NonZeroIndex=find(NonZeroFlag);

t=diff([0, NonZeroIndex]);

index=find(t-1);

Pos=NonZeroIndex(index)

CheckValue=v(Pos)