MATLAB: How to find the sequences with length bigger than n in a vector

lenghtvector

Dear, I have a vector and I need to find the sequences of consecutive numbers with length greater than or equal to 6. For example:

v = [1 2 3 4 5 6 7 10 12 16 17 18 19 20 21 24 25 30 31 32 33 34 35 36]

I would like to leave only the sequences greater than or equal to 6.

Then I would get:

r = [1 2 3 4 5 6 7 16 17 18 19 20 21 30 31 32 33 34 35 36]

Here is a part of my vector:

v = [342  344  345  346  348  351  352  353  354  355  356  357  358  359  427  428  429  430  431  432  433  434  435  436  437  438  443  444  445  446  447  448  449  450  581  582  591  881  945  947  948  949  1013  1014  1016  1018  1019  1020  1021  1022  1023  1024  1025  1026  1027  1028  1029  1030  1031  1032  1033  1034  1035  1036  1037  1038  1039  1040  1085  1100  1172  1173  1174  1175  1176  1177  1178  1179  1181  1186  1562  1581  1591  1592  1594  1595  1610  1611  1612  1626  1679  1810  1811  2064  2077  2087  2103]

If someone can help me, I'll be very grateful.

Best Answer

v = [1 2 3 4 5 6 7 10 12 16 17 18 19 20 21 24 25 30 31 32 33 34 35 36]
minlength = 6;
isconsecutive = diff(v ) == 1;
seqedges = find(diff([false, isconsecutive, false]));
seqstarts = seqedges(1:2:end);
seqstops = seqedges(2:2:end);
seqlengths = seqstops - seqstarts + 1;
tokeep = seqlengths >=  minlength
indicestokeep = cell2mat(arrayfun(@(s, e) s:e, seqstarts(tokeep), seqstops(tokeep), 'UniformOutput', false);
filteredv = v(indicestokeep)

Related Solutions

MATLAB: Max value in a repetitive vector

maxes = [vec( diff( vec ) < 0 ), vec(end)];

works if it is as structured as your example always, where vec is your vector. If it isn't always an increasing set of sequences like that please give an example of a more general kind.

MATLAB: How count NaN values and replace NaNs in a sequence with that number

I don't think it's entirely possible to do it without a loop, but the loop can be limited to the number of sequences (3 steps in your example)

v = [0 0 NaN 0 0 NaN NaN NaN 0 0 0 0 0 NaN];
seqedges = find(diff([false, isnan(v), false]));
seqstarts = seqedges(1:2:end);
seqends = seqedges(2:2:end);
seqlengths = seqends - seqstarts;
for seq = 1:numel(seqstarts)
  v(seqstarts(seq):seqends(seq)-1) = seqlengths(seq);
end

edit: actually, it's possible without a loop:

v = [0 0 NaN 0 0 NaN NaN NaN 0 0 0 0 0 NaN];
nanlocs = isnan(v);
seqedges = find(diff([false, nanlocs, false]));
seqlengths = seqedges(2:2:end) - seqedges(1:2:end);
v(nanlocs) = repelem(seqlengths, seqlengths)

Best Answer

Related Solutions

MATLAB: Max value in a repetitive vector

MATLAB: How count NaN values and replace NaNs in a sequence with that number

Related Question