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Dear all, I have a data frame of 2160 rows and 4320 columns, which I hope to condense to a smaller dataset by finding averages of 6 by 6 blocks of values (to produce a data frame of 360 rows by 720 columns). How would I go about finding the mean of a 6 x 6 block, then find the mean of the next adjacent 6 x 6 block, and so on, until the whole data frame has been covered? One slight twist is that

# Dear R Community, # I have this data frame: df1 <- data.frame( F1 = factor( c( rep("D1",12),rep("D2",12),rep("D3",12) ) ), F2 = factor( rep( rep( paste("O",1:6,sep=""), rep(2,6) ), 3) ), F3 = factor( rep( c("V1","V2"), 18 ) ), S1 =