MATLAB: Data Analysis: Can I compare and match timestamps

compare datadataMATLABtimestamp

I have imported in Matlab 2 sets of big data (each set consist 2 columns by 8000 rows). The first set consist of a timestamp (date, time) and data type A and the second set consist of timestamp (date, time) and data type B. Is it possible that I program MATLAB to compare the 2 timestamps from the different sets and put data A and B in the correlated rows?

Best Answer

I think you are looking for something like join or outerjoin for tables.

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MATLAB: Image Analysis: measuring cusping and roughness

Here's how I would approach it:

% Read the image and convert to BW mask of peaks
I_orig = imread('cusp_micro.jpg');
I = rgb2gray(I_orig);
BW_peaks = im2bw(I);
% How far is every non-peak pixel from its nearest peak?
distFromPeaks = bwdist(BW_peaks);
% Let's only choose pixels further from a peak than any of its neighbours
maxDistsMask = imregionalmax(distFromPeaks);
[trI,trJ] = find(maxDistsMask);
trVals = I(maxDistsMask);
tr2pkDists = distFromPeaks(maxDistsMask);
% Now loop over each trough and find the image intensity of its nearest
% peak (add 5 pixels padding so we choose the max from a few nearby peaks)
pkInds = find(BW_peaks);
[pkI,pkJ] = ind2sub(size(BW_peaks),pkInds);
trPartnerPkVals = zeros(size(trI));
for i = 1:length(trI)
    tr2allPkDists = sqrt((pkI-trI(i)).^2 + (pkJ-trJ(i)).^2);
    withinRangeMask = tr2allPkDists < (tr2pkDists(i) + 5);
    trPartnerPkVals(i) = max(I(pkInds(withinRangeMask)));
end
% Display what we've got:
I_norm = double(I)/double(max(I(:)));
figure, imshow(cat(3,I_norm,max(BW_peaks, I_norm),I_norm)), hold on
plot(trJ,trI,'m.')
% Now if we look at all of the maxdists in the image, how far away from
% peaks are they?
figure, plot(sort(tr2pkDists)), title 'Distribution of cusp spacing'
figure, plot(sort(trPartnerPkVals - double(I(maxDistsMask))))
title 'Distribution of roughness'

So the largest trough2pk distance (or cusp spacing) is around 40 pixels. Notice of course that there are a range of pk2trough values depending on where you look in the image, likewise measures of roughness. You may need a scheme to select maximum cusp spacing or roughness within an X-pixel radius of an area you're interested in, or something similar.

Thanks, Sven.

MATLAB: How to match the table

Have you tried join?

%in the future make it easy to use your example in code by using valid matlab syntax
t1 = table({'Mek', 'Lahi', 'Raju', 'Ram', 'Krish', 'Mek', 'Ram', 'Balu', 'Raju'}.', num2cell('SSFSFFSSS').', 'VariableNames', {'Key', 'Value'}) 
t2 = table({'Mek' 'Lahi' 'Raju' 'Ram' 'Krish' 'Balu'}.', {'VAL' 'HAT' 'KJI' 'GAT' 'HTY' 'KTY'}.', 'VariableNames', {'Key', 'OtherValue'})
join(t1, t2)

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MATLAB: Image Analysis: measuring cusping and roughness

MATLAB: How to match the table

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