Hi
I have a dataframe as below:

x1    y1    x2    y2    x3    y3    output
2    100    190    99    1430    79    89
2    100    192    63    1431    75    69
2    100    192    63    1444    51    57
3    0    195    99    1499    50    74.5
3    0    198    98    1500    80    89
30    0    198    100    1451    97    65.66666667
32    100    868    100    1451    97    99
33    82    870    100    1490    97    93
33    0    871    82    1494    85    55.66666667


In reality the dataframe has pairs of columns x & y up to a large number.
As you can see from the column labelled output in the dataframe; I want to
calculate the mean of each row of the yn columns, but only to include each
yn value in the calculation of the mean if the corresponding xn column
value is greater than 10.
So for row 1; you will see that only y2 & y3 are included in calculating
the output column, but for row 6 y1-y3 are all included.
Because the number of paired x & y columns is large I am not sure the best
way to achieve this.
Thanks in advance
Tom

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