How can I determine the indices and length of consecutive non-NaN values in an array?

Say I have a vector A = [NaN NaN NaN 10 22 NaN 33 28 21 NaN 20 98 NaN], how do I:

1) determine the indices of consecutive non-NaN values; and

2) extract the count and length of these 'consecutive events'

Thank you!

Answer 1

[Stephan]

1. FInd the indexes:

B = find(isnan(A))

2. To find consecutive blocks you could use the diff function on a logical array:

C = isnan(A) % gives a logical array
diff(C)      % --> is different from zero, when a block changes (1 for start and -1 for end of block)

[Jonathan Macuroy]

Hello, I think this is the simplest method. Thank you very much!

[Stephen23]

Note that the code Stephan shows to "find consecutive blocks" will not detect when the non-NaN blocks occur at the ends of the vector.

Answer 2

[Stephen23]

1)

>> A = [NaN NaN NaN 10 22 NaN 33 28 21 NaN 20 98 NaN];
>> find(~isnan(A))
ans =
    4    5    7    8    9   11   12
 

or do you mean something else by "consecutive non-NaN values" ? Do you only want to get the indices at the beginning+end of each run of non-NaNs ?

2)

>> D = diff([false,~isnan(A),false]);
>> L = find(D<0)-find(D>0) % length
L =
   2   3   2
>> N = numel(L) % count
N =  3

[Jonathan Macuroy]

Hello! Thank you very much for your answer, yes I was referring to your second code. :)