MATLAB: Removing consecutive zeros of a certain length

consecutive zerodatadeletedurationzerozeros

Hi everyone,

I have data consisting of two columns: time and counts. The counts data consists of multiple numbers with some consecutive zeros. How can Matlab find and count the duration of these consecutive zeros and then delete the rows of them if the duration is above a certain value?

Best Answer

 x = [0 0 0 2 2 0 0 0 3 3 3 3 3 0 0 0 0 ]' ;
transitions = diff([0 ;x == 0; 0]); %find where the array goes from non-zero to zero and vice versa
runstarts = find(transitions == 1);
runends = find(transitions == -1); %one past the end
runlengths = runends - runstarts;
% keep only those runs of length 4 or more:
runstarts(runlengths > 3) = [];
runends(runlengths > 3) = [];
%expand each run into a list indices:
indices = arrayfun(@(s, e) s:e-1, runstarts, runends, 'UniformOutput', false);
indices = [indices{:}];  %concatenate the list of indices into one vector
% Remove those zeros which are consecuitve 3 in number
x(indices) = [] ;

Code taken from here: https://in.mathworks.com/matlabcentral/answers/293926-how-do-i-find-4-or-more-consecutive-zeros-and-replace-these-zero-s

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MATLAB: Remove duplicate variables depending on a second variable

Hi Marty,

Try the code below.

% Defining ppn (all at once)
ppn = [ {'BG1026';'BG1027';'BG1028';'BG1028';'BG1028';'BG1029';...
    'BG1030';'BG1030';'BG1030';'BG1030'},... % start col 2
    {'0';'0';'1';'0';'0';'1';'1';'0';'1';'0'},... % start col 3
    {'1.2';'2.2';'1.3';'0.2';'8.9';'3.4';'3.0';'0.3';'1.3';'0.3'}];
% Storing ppn column 2 as numerical values
bPpn=cell2mat(cellfun(@(c)str2double(c),ppn(:,2),...
    'UniformOutput',false));
% Deleting all duplicates with 0 in bPpn
idx = strcmp(ppn(1:end-1,1),ppn(2:end,1));
delidx = ([idx;false] | [false;idx]) & ~bPpn;
ppn(delidx,:)=[];
clear bPpn idx delidx;
% Get names of remaining duplicates
chooseNames = ppn([strcmp(ppn(1:end-1,1),ppn(2:end,1));false],1);
% Loop over chooseNames and keep one at random
if numel(chooseNames)>0,
    for j=1:numel(chooseNames),
        dupidx=find(strcmp(chooseNames{j},ppn(:,1)));
        dupidx(randi(numel(dupidx)))=[];
        ppn(dupidx,:)=[];
    end,
end,

Hope this helps.

MATLAB: How to find 4 or more consecutive zeros and replace these zero’s

Here is one way to do it, which does not involve looping over the whole vector (only over each run of zero)

transitions = diff([0; x == 0; 0]); %find where the array goes from non-zero to zero and vice versa
runstarts = find(transitions == 1);
runends = find(transitions == -1); %one past the end
runlengths = runends - runstarts;
%keep only those runs of length 4 or more:
runstarts(runlengths < 4) = [];
runends(runlengths < 4) = [];
%expand each run into a list indices:
indices = arrayfun(@(s, e) s:e-1, runstarts, runends, 'UniformOutput', false);
indices = [indices{:}];  %concatenate the list of indices into one vector
x(indices) = 2 %replace the indices with 2

Best Answer

Related Solutions

MATLAB: Remove duplicate variables depending on a second variable

MATLAB: How to find 4 or more consecutive zeros and replace these zero’s

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