MATLAB: How to create a vector with specified blanks

blankvector

Hi,I have a time series of daily data for 4 years(4*365 data) and I would like to have a some of daily data to be blanks(gaps) to do some analysis on the rest. My problem is that how I can create a specified length gaps,for example 3 days,on my vector data.Is there any script to create artificial gaps with specific gap length?

Best Answer

Rita: Seems like you're having trouble so I put together this code for you:
% First we need to create sample data.
data = randi(9, 1, 300) % Create sample data.
% Get location of nans to put into the original sample data.
originalNanLocations = sort(randperm(length(data)-3, 10)) % Make 10 originall nans
data(originalNanLocations) = nan;
% Now we have our original data and we can begin...
% Find out where the original nans are, so we don't place other nans next to them
originalNanLocations = isnan(data);
% Find out how many nans we need to be in there.
% It should be about 10% of the number of elements.
numRequiredNans = floor(0.1 * length(data))
% Assign nans.  Note, there may be overlap so that some stretches may be more than 3 long.
numNansCurrently = 0;
% Create a failsafe so we don't get into an infinite loop
maxIterations = 1000000;
iterationNumber = 1;
% Now loop, placing nans, until we get the required number of nans in the data.
while numNansCurrently < numRequiredNans && iterationNumber <= maxIterations
  % Get location of starts of 15 "new" nan runs
  nanStartLocation = randi(length(data)-4) + 1;
  % Find the ending indexes of each run
  nanEndLocation = nanStartLocation + 2;
  % Get data from the start to the end plus one on either side of it.
  % so we don't place other nans next to them, 
  % since that would create a stretch of 4 or more.
  thisData = data((nanStartLocation-1):(nanEndLocation+1));
  % Now find if out where the original nans are, 
  if any(isnan(thisData))
    % Nans were found - skip this stretch of data.
    continue;
  end
  % If we get here no nans were found in that location
  % and we are free to assign new nans there.
  data(nanStartLocation:nanEndLocation) = nan;
  % Count the number of nans we have
  numNansCurrently = sum(isnan(data));
  iterationNumber = iterationNumber + 1;
end
data % Print to command window.
% Now the original nans will still be there and not be adjacent
% to any of the "new" nan stretches of three nans in a row.
% And the overall number of nans will be 10% of the elements
% or not more than 2 more than that.
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