matlab - How to count non zero elements in a vector and replace this values based the number of occurences -

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• finding islands of zeros in sequence 7 answers

i'm new matlab user , in case have vector let say:

v = [0 0 0 0.1 0.2 0.3 0.4 0.5 0 0 0 0 0 0 0.1 0.2] 

i want count consecutive non 0 values i.e in vector have first 5 nonzero values [0.1 0.2 0.3 0.4 0.5] , 2 last nozeros values [0.1 0.2]

what want is: count consecutive non 0 values , put condition i.e. if length of nonzeros greater 3 (count>3) respective values of vector v(i) remain v(i) if length consecutive values less 3 (count<3) respective values of v(i) = 0

i want new vector let v1 derivated vector v where:

v1 = [0 0 0 0.1 0.2 0.3 0.4 0.5 0 0 0 0 0 0 0 0] 

any appreciated.

if have matlab image processing toolbox, can use power of morphological operations. morphological opening (imopen) removes objects smaller structuring element image. can use in 2d , use [1,1,1] structuring element remove objects, i.e. sequences of nonzero elements, shorter 3:

first make sequence binary: 0 or nonzero.

w = v~=0; 

then zero-pad sequence, short nonzero sequences @ borders eliminated. use [1,1,1] structuring element, zero-padding 1 sufficient:

w = [0,w,0]; 

now opening remove small nonzero sequences

w1 = imopen(w, [1,1,1]); 

the vector w1 contains 0 if corresponding element in v or should set 0 , 1 if value should kept. result v1, can ignore first , last entry (those elements zero-padding), , multiply input, e.g. 1 * 0.1 = 0.1:

v1 = w1(2:end-1) .* v; 

which gives correct result without loop, if statement or such stuff! 4 simple operations: morphology , bit of multiplication , zero-padding.