I have some issue while passing contrast argument as a vector. I create a vector

contrasts <- c("TT-C,D-C,DT-C,D-TT,DT-TT,DT-D")

after removing double quotes from the above vector by

noquote(contrasts)

I pass it to

contrast.matrix <- makeContrasts(contrasts,levels=design)

to construct a contrast matrix, which gives an error:

Error in cm[, j] <- ej :
  number of items to replace is not a multiple of replacement length

If i use

contrast.matrix <- makeContrasts(TT-C,D-C,DT-C,D-TT,DT-TT,DT-D,levels=design)

it works nicely. May i know what is going wrong. Thanks

Look at ?makeContrasts and read the code example. The last two lines show you exactly how to do what you want.