Calculate within and between variances and confidence intervals in R

Question

I need to calculate the within and between run variances from some data as part of developing a new analytical chemistry method. I also need confidence intervals from this data

Answer 1

If you want to apply a function (such as var) across a factor such as Run or Rep, you can use tapply:

> with(variance, tapply(Value, Run, var))
          1           2           3           4 
0.005833333 0.310000000 0.610000000 0.043333333 
> with(variance, tapply(Value, Rep, var))
          1          2          3 
0.48562500 0.88729167 0.05583333