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How to combine indexing?

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Markus Gschwind
Markus Gschwind on 10 Oct 2020
Edited: Sindar on 13 Oct 2020
Is there an elegant way of combining two indexings to select time points from a long time-series?
I have independent selection criteria :
  1. marked events (index vector ind_Ev)
  2. marked artifacted periods (ind_Art)
I would like to combine both to select the elements of a time series with 500000 elemtents, i.e. take the ind_Ev and exclude the ind_Art (ind_Ev & ~ind_Art), however, they can point to the same element, in which case it will be excluded.
Thank you so much,
Markus

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Answers (1)

Sindar
Sindar on 10 Oct 2020
Edited: Sindar on 10 Oct 2020
There may be a better way, but this should work:
% set up a logical-indexing vector that selects no elements
idx_Ev_not_Art = false(500000,1);
% add all ind_Ev elements
idx_Ev_not_Art(ind_Ev) = true;
% remove all ind_Art elements
idx_Ev_not_Art(ind_Art) = false;
% extract those elements
data_Ev_not_Art = data(idx_Ev_not_Art);

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Sindar
Sindar on 13 Oct 2020
If you want to exclude artifacts, use the blocks "to affect the original extraction"
% set up a logical-indexing vector that selects no elements
idx_Ev_not_Art = false(500000,1);
% add all elements from ind_Ev OR ind_period [intesect for AND]
idx_Ev_not_Art( union(ind_Ev,ind_period) ) = true;
% remove all ind_Art elements
idx_Ev_not_Art(ind_Art) = false;
% extract those elements
data_Ev_not_Art = data(idx_Ev_not_Art);
That error suggests that your ind_Ev is not a set of indices (1,2,40,etc.). More likely than it being a numeric logical vector (0 1 1 0 0 1) is that something else has gone wrong. Can you print the first 10 elements and comment here?
ind_Ev(1:10)
Markus Gschwind
Markus Gschwind on 13 Oct 2020
>> That error suggests that your ind_Ev is not a set of indices (1,2,40,etc.). More likely than it being a numeric logical vector (0 1 1 0 0 1) is that something else has gone wrong. Can you print the first 10 elements and comment here?
Yes, you were right! It was not [1,3,120,400 etc.] but [1 0 0 1 0 0 0 0 etc.]. When using the first it works without "logical", when using the second, I need "logical".
Sindar
Sindar on 13 Oct 2020
Oh, I'd assumed you had indices, not logicals. There are faster ways in that case, since you can do the boolean logic directly:
idx_Ev = logical(ind_eV);
idx_period = logical(ind_period);
idx_Art = logical(ind_Art);
% data from either events, periods, or both. No artifacts
data_EvORPer_not_Art = data( (idx_Ev | idx_period) & ~idx_Art );
% data from overlap of both events and periods. No artifacts
data_EvANDPer_not_Art = data( idx_Ev & idx_period & ~idx_Art );
% data from events excluding artifacts, plus periods regardless
data_EvANDPer_not_Art = data( (idx_Ev & ~idx_Art) | idx_period );

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