[R] average of y at each level of x?

[Liaw, Andy]

Try (untested):

p1 <- tapply(y, x, function(z) mean(z == 0))

HTH,
Andy

> From: Bill Simpson [mailto:William.Simpson at drdc-rddc.gc.ca] 
> 
> I have x,y data and would like to compute the average of y at 
> each level 
> of x.
> 
> > x
>  [1] 0.006110 0.007027 0.007027 0.007027 0.008081 0.008081 
> 0.008081 0.008081  [9] 0.008081 0.008081 0.008081 0.009293 
> 0.009293 0.009293 0.009293 0.009293 [17] 0.009293 0.009293 
> 0.009293 0.010686 0.010686 0.010686 0.010686 0.010686 [25] 
> 0.010686 0.010686 0.010686 0.010686 0.010686 0.012289 
> 0.012289 0.012289 [33] 0.012289 0.012289 0.012289 0.012289 
> 0.012289 0.012289 0.012289 0.012289 [41] 0.012289 0.012289 
> 0.014133 0.014133 0.014133 0.014133 0.016253 0.018691 [49] 
> 0.021494 0.024718 0.028426 0.032690 0.037594 0.043233 
> 0.049718 0.057175 [57] 0.065752 0.075614 0.086957 0.100000
> 
> > y
>  [1] 0 0 1 0 0 1 0 1 1 0 1 1 1 0 1 0 1 0 1 0 1 1 0 1 1 0 1 0 
> 1 1 1 0 1 1 1 1 1 1 [39] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
> 
> > table(x,y)
>           y
> x          0  1 
>   0.00611   1  0
>   0.007027  2  1
>   0.008081  3  4
>   0.009293  3  5
>   0.010686  4  6
>   0.012289  1 12
>   0.014133  0  4
>   0.016253  0  1
>   0.018691  0  1
>   0.021494  0  1
>   0.024718  0  1
>   0.028426  0  1
>   0.03269   0  1
>   0.037594  0  1
>   0.043233  0  1
>   0.049718  0  1
>   0.057175  0  1
>   0.065752  0  1
>   0.075614  0  1
>   0.086957  0  1
>   0.1       0  1
> 
> I would like to compute p = count1/(count0 +count1). For 
> example, for x=0.012289, p= 12/(1+12)= 0.923077. Please tell 
> me how to do it. Maybe 
> there is a better way to do this without going through table().
> 
> Thanks very much for any help.
> 
> Bill Simpson
> 
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