Obtaining absolute deviation from mean for two sets of scores

Question

To obtain absolute deviation from the mean for two groups of scores, I usually need to write long codes in R such as the ones shown below.

Question

I was won

Answer 1

How about

score <- lapply(split(y, groups), FUN = function (u) abs(u - mean(u)))

or

score <- ave(y, groups, FUN = function (u) abs(u - mean(u)))

The results are organized in a different way. Choose the one that is most comfortable to you.

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There is something wrong with your wording. mad returns a single statistic / value for data. For example,

sapply(split(y, groups), mad)

You are not vectorizing mad, but simply computing the deviation for each datum as your example code shows.