matlab - dynamically fill vector without assigning empty matrix -


oftentimes need dynamically fill vector in matlab. sligtly annoying since first have define empty variable first, e.g.:

[a,b,c]=deal([]); ind=1:10   if rand>.5 %some random condition emphasize dynamical fill of vector     a=[a, randi(5)];   end end %display result

is there better way implement 'push' function, not have define empty vector beforehand? people tell me nonsensical in matlab- if think case please explain why.

related: push variable in vector in matlab, is-there-an-elegant-way-to-create-dynamic-array-in-matlab

in matlab, pre-allocation way go. docs:

for , while loops incrementally increase size of data structure each time through loop can adversely affect performance , memory use.

as pointed out in comments m7913d, there question on mathworks' answers section addresses same point, read here.

i suggest "over-allocating" memory, reducing size of array after loop.

numloops = 10; = nan(numloops, 1); ind = 1:numloops     if rand > 0.5         a(ind) = 1; % assign value current loop index     end end = a(~isnan(a)); % rid of values weren't used (and remain nan)

no, doesn't decrease amount have write before loop, it's worse having write a = []! however, you're better off spending few keystrokes , minutes writing structured code making saving , having worse code.


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