[R] how to 'average' one col wrt to another one

From: YI LIU <liuyi.feier_at_gmail.com>
Date: Wed, 16 Jun 2010 18:28:24 -0700

Hi, folks,




The code will generate a sample dataset. I have thousands rows of data.

For the same 'leave' and 'arrive', how can I get the sum of square of percentages of 'line' for each combination of 'leave' and 'arrive'?

For the sample dataset, we have 5 combinations of 'leave' and 'arrive', namely, 'ab', 'ef'

For 'ab', the line can be 'c' or 'i'. 1st row, it is line 'i' (1/3), and 5&6th row (2/3), it is line 'c'. then the sum of square of percentage for 'ab' is (1/3)^2+(2/3)^2=0.56

For 'ef', it is 0.5^2+0.5^2=0.5

I would like the final dataset to be like as follows:

ab 0.56
ef 0.5

How to achieve it?


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