hi guys! i have two columns and i want to sum the second columns based on values of the first column. for example, the two columns are:
3 0.287000000000000
3 0.303000000000000
3 0.309000000000000
3 0.287000000000000
2 0.732000000000000
1 0.3380000000
the matrix is 8784*2. so, i want to sum the second column in the three different cases: when the first column is 1,sum all the values corresponding to 1, when 2 and 3 i want to do the same. how can i do? someone can help me?
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