[R] data transformation

From: ronggui <0034058_at_fudan.edu.cn>
Date: Sun 05 Jun 2005 - 11:50:56 EST


i have data fame da:
> da

    x y
1 1 a
2 2 a
3 3 a

4 4 a
5 5 a
6 6 b
7 7 b
8 8 b
9 9 b
10 10 b
> str(da)

`data.frame': 10 obs. of 2 variables:  $ x: num 1 2 3 4 5 6 7 8 9 10
 $ y: Factor w/ 2 levels "a","b": 1 1 1 1 1 2 2 2 2 2

and i want to generate new variable da$z,when y=="a",da$z=da$x-mean(x[y=="a"]) ,when y=="b",da$z=da$x-mean(x[y=="b"]).

this data frame is simple and i can do it by hand,if the y has many levels and i have x1,x2.... can i do it quickly?



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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jun 05 11:55:20 2005

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