How to count number of specific value?

I have a matrix and I'm trying to count the number of a specific value in rows (i.e. < 4 )

for example 5 2 3 8 7 1 2 2 3

nnz( A(1,:) < 4); --> 6

but I want sth like this 2 and 4

Answer 1

[Image Analyst]

If you have the Image Processing Toolbox, use bwlabel and regionprops:

A = [5 2 3 8 7 1 2 2 3]
[labeledA, numRegions] = bwlabel(A < 4)
% Get the size of the regions.
props = regionprops(labeledA, 'Area')
elementCounts = [props.Area]

Run the demo and you'll see this in the command window:

A =
     5     2     3     8     7     1     2     2     3
labeledA =
     0     1     1     0     0     2     2     2     2
numRegions =
     2
props = 
  2×1 struct array with fields:
    Area
elementCounts =
     2     4

[Justyna Slawska]

And tell me how to get this specific value (2 3 and 1 2 2 3)

Answer 2

[Geoff Hayes]

Justyna - if

 data = [5 2 3 8 7 1 2 2 3]

then you can use length and https://www.mathworks.com/help/matlab/ref/find.html to determine the number of elements less than four

 length(find(data<4))

[Justyna Slawska]

in this way I get the result 6, but I want 2 and 4