MATLAB: How to create a new matrix with daily averages given hourly data

averagedaily averagedaily meanMATLABmean

I have data of date numbers 'y' value for each hour of the day. how do I create a matrix of date number as an 'x' value and a single daily average for 'y' value? Sample data included below
if true
  % code
end
721473  1.920
721473  2.150
721473  2.160
721473  1.940
721473  1.610
721473  1.180
721473  0.820
721473  0.610
721473  0.560
721473  0.710
721473  1
721473  1.400
721473  1.690
721473  1.860
721473  1.880
721473  1.730
721473  1.410
721473  1.040
721473  0.700
721473  0.440
721473  0.400
721473  0.510
721473  0.790
721474  1.140
721474  1.570
721474  1.940
721474  2.110
721474  2.090
721474  1.890
721474  1.600
721474  1.240
721474  0.960
721474  0.780
721474  0.760
721474  0.900
721474  1.260
721474  1.540
721474  1.720
721474  1.760
721474  1.690
721474  1.490
721474  1.180
721474  0.840
721474  0.600
721474  0.520
721474  0.600
721474  0.820

Best Answer

There are several ways.
One option:
M = [721473  1.920
          ...
     721474  0.820];
[M1u,~,ix] = unique(M(:,1));
DailyMean = accumarray(ix, M(:,2), [], @(x)mean(x));
Result = [M1u DailyMean]
Result =
                    721473           1.2395652173913
                    721474          1.29166666666667
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