Description Usage Arguments Value Author(s) Examples
MSbetAvg calculates the mean-square-between contrast according to the design vector. Responses for each condition are averaged, and the sample variance is calculated for these averages.
1 | MSbetAvg(dat, avgmat)
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dat |
The vector of measurements on which the constrast is computed. |
avgmat |
The design parameters, as extracted by getAveraging(). |
The value of the quadratic contrast computed on the data vector.
Yuval Benjamini
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | data(fMRI_responses,design_vec)
msbet = MSbetAvg(fMRI_responses[1,], getAveraging(design_vec))
# Compute same value using "aov" when design is balanced ...
ns =tapply(design_vec,design_vec, length)
# (check that design is balanced)
stopifnot(length(unique(ns))==1)
m = length(unique(design_vec))
aov_sum = summary(aov(fMRI_responses[1,] ~ factor(design_vec)))
ss_bet = aov_sum[[1]][1,2]
# In unbalanced designs, each example should require more care...
msbet_aov = (ss_bet / ns[1] )/(m-1)
cat(msbet, msbet_aov)
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