3 views (last 30 days)
ali hassan on 12 Feb 2022
Edited: DGM on 12 Feb 2022
assume i have a vector array:
a=[1 1 1 0 0 1 1 1]
how can i put loop such that if sum of any three successive elements is equal to 3, it prints 'ali'.
can it be done without loops?
Austin Decker on 12 Feb 2022
Well, MATLAB is likely looping behind the scenes, but you could do this:
a = [1,1,1,0,0 1,1,1];
ind1 = 1:length(a) -2;
ind2 = ind1 + 2;
result = arrayfun(@(x,y) sum(a(x:y)),ind1,ind2);
qty = sum(result == 3);
disp(join(repmat("ali",qty,1),newline));

DGM on 12 Feb 2022
Edited: DGM on 12 Feb 2022
This works easily enough. After R2016a, you can do the same with movsum().
a = [1 1 1 0 0 1 1 1];
if any(conv(a,[1 1 1],'valid')==3)
fprintf('ali\n')
end
ali
DGM on 12 Feb 2022
Edited: DGM on 12 Feb 2022
To omit nans:
a = [2 nan 1 1 0 0 nan 1 1 nan 1];
% using movsum
s = movsum(a,3,'omitnan');
any(s(2:end-1)==3)
ans = logical
1
% using conv
a(isnan(a)) = 0;
s = conv(a,[1 1 1],'valid');
any(s==3)
ans = logical
1
If the value range of a never extends beyond [0 1], then you could also simply treat any propagated NaNs as 0. This is simply because it wouldn't be possible to have a sum equal to 3 if the window size were also 3 and any element were anything other than 1.
a = [1 nan 1 1 0 0 nan 1 1 nan 1];
s = conv(a,[1 1 1],'valid') % this will pass NaN
s = 1×9
NaN NaN 2 1 NaN NaN NaN NaN NaN
any(s==3) % NaNs aren't equal to 3
ans = logical
0