Finding Closest Data Point

2016 10 25
2 个回答
回答已采纳
更新时间：2016 10 26
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0 个投票

I have one matrix with data in the first column and time stamps in the second column (datamatrix.mat). The next matrix contains spiketimes (spiketimematrix.mat). I want to get the data point in the first column of first matrix that is the closest time point corresponding to the spike times in spiketimematrix.mat. For example, the first spiketime is 166.1670, which corresponds to the closet time point of 166.1696 and corresponds with the data point 2.5281.

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 采纳的回答

Image Analyst
Image Analyst 2016-10-25

0 个投票

Try something like
% Find all time differences:
timeDiffs = abs(timeStamps - spikeTimes);
% Find out which has the smallest difference:
[minTimeDiff, indexOfMin] = min(timeDiffs);
% Get the value from column 1.
result = dataColumn1(indexOfMin)

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Krispy Scripts
Krispy Scripts 2016-10-25
timeStamps and spikeTimes are different sizes so I am not sure that it is possible.
Image Analyst
Image Analyst 2016-10-25
编辑：Image Analyst 2016-10-26
Oh, they're not synced up. Then you should use pdist2 like Roger suggested, if you have the Statistics and Machine Learning Toolbox. Look for the smallest non-zero value.
Krispy Scripts
Krispy Scripts 2016-10-25
I am confused on how the row, column outputs can be used to find the those corresponding data points?
Krispy Scripts
Krispy Scripts 2016-10-25
Would this be simpler if instead of getting the closest, I got the one greater than or equal to?
Image Analyst
Image Analyst 2016-10-26
Sorry - that's what I get for tossing something off the top of my head and not actually testing it. Ignore that code (I'll delete it) and use this instead:
numPoints1 = 6;
timeStamps = rand(numPoints1, 1) % Sample data.
numPoints2 = 3;
spikeTimes = rand(numPoints2, 1) % Sample data.
t1 = [timeStamps, zeros(length(timeStamps), 1)];
t2 = [spikeTimes, zeros(length(spikeTimes), 1)];
distances = pdist2(t1, t2)
minDistance = min(distances(distances>0))
[row, column] = find(distances == minDistance)
fprintf('The minimum time difference is %f and goes between\n timeStamp(%d) = %f, and\n spikeTimes(%d) = %f\n',...
minDistance, row, timeStamps(row), column, spikeTimes(column));

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Roger Stafford
Roger Stafford 2016-10-25

1 个投票

I recommend you use the ‘pdist2’ function using the “Smallest” option. It is described at:
https://www.mathworks.com/help/stats/pdist2.html

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