[R] Manually calculating values from aov() result

[Brian Smith]

Hi,

I have performed ANOVA as below

dat = data.frame(
'A' = c(-0.3960025, -0.3492880, -1.5893792, -1.4579074, -4.9214873,
-0.8575018, -2.5551363, -0.9366557, -1.4307489, -0.3943704),
'B' = c(2,1,2,2,1,2,2,2,2,2),
'C' = c(0,1,1,1,1,1,1,0,1,1))

summary(aov(A ~ B * C, dat))

However now I also tried to calculate SSE for factor C

Mean = sapply(split(dat, dat$C), function(x) mean(x$A))
N = sapply(split(dat, dat$C), function(x) dim(x)[1])

N[1] * (Mean[1] - mean(dat$A))^2 + N[2] * (Mean[2] - mean(dat$A))^2
#1.691

But in ANOVA table the sum-square for C is reported as 0.77.

Could you please help how exactly this C = 0.77 is obtained from aov()