weighted average method for rates

[duo wan <duo_wan@yahoo.com>]

Dear S-users:

I am trying to combine the rates using common weighted average methods. is anyone who knows how to use S to do it or assist me with formulaes?

thanks!!!

duowan

num_im=num of improved patients;

num_pat=number of patients.

rate=num_im/num_pat

Obs num_im num_pat RATE

1 16.0 17 0.94118

2 10.0 12 0.83333

3 4.0 8 0.50000

4 43.0 58 0.74138

5 9.5 10 0.95000

6 25.0 42 0.59524

7 13.0 14 0.92857

8 11.5 12 0.95833

9 22.0 41 0.53659

10 4.0 5 0.80000

11 5.0 6 0.83333

12 18.0 23 0.78261

13 58.0 68 0.85294

14 6.0 10 0.60000

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