MATLAB: Select data from a text file

selecting datatext file

Matlab users,
I have a question regarding selecting certain data from a text file. First of all I need to find all rows where the values in first and second columns are the same (measurement epoch). Then I have to calculate the arithmetic mean of the values in fourth, fifth and sixth columns (for the identified “the same” rows). Finally I want to save in the output file “age of observation: values from first and second column" and corresponding to them arithmetic mean. Below there is attached a small piece of the input file.
Does anyone have any suggestions on how I might be able to do this?
Many thanks!
 0 50  1  -0.20   0.92  -1.95
 0 55  1  -0.20   0.94  -1.97
 1  0  1  -0.21   0.95  -2.00
 1  5  1  -0.33   0.66  -1.86
 1 10  1  -0.33   0.68  -1.88
 1 15  1  -0.38   0.66  -1.98
 1 20  1  -0.38   0.67  -2.00
 1 25  1  -0.44   0.65  -2.13
 1 30  1  -0.44   0.25  -1.51
 1 35  1  -0.44   0.26  -1.52
 1 40  1  -0.48   0.30  -1.69
 1 45  1  -0.48   0.30  -1.70
 1 50  1  -0.51   0.31  -1.79
 1 55  1  -0.51   0.31  -1.79
 2  0  1  -0.57   0.32  -1.96
 2  5  1  -0.57   0.32  -1.95
 2 10  1  -0.62   0.30  -2.04
 2 15  1  -0.62   0.29  -2.03
 1 50  2  -0.22   1.33  -2.61
 1 55  2  -0.22   1.34  -2.64
 2  0  2  -0.35   1.23  -2.81
 2  5  2  -0.28   1.15  -2.50
 2 10  2  -0.28   1.16  -2.52
 2 15  2  -0.23   1.11  -2.29
 2 20  2  -0.28   0.74  -1.85
 2 25  2  -0.28   0.75  -1.86
 2 30  2  -0.28   0.71  -1.81
 2 35  2  -0.28   0.72  -1.82
 2 40  2  -0.29   0.70  -1.83
 2 45  2  -0.29   0.71  -1.83
 2 50  2  -0.33   0.69  -1.91

Best Answer

Reading the file is easy with dlmread or readtable.
For calculating the means of identical epoch, you can use the Split-Apply-Combine workflow introduced in R2015b, or unique with accumarray:
 [epoch, ~, subs] = unique(m(:, [1 2]), 'rows'); %find unique epochs as rows of column 1 and 2
 meancol5 = accumarray(subs, m(:, 5), [], @mean); %mean of column 5 by epoch
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