diff - R how can I calculate difference between rows in a data frame -

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here simple example of problem:

> df <- data.frame(id=1:10,score=4*10:1) > df        id score     1   1    40     2   2    36     3   3    32     4   4    28     5   5    24     6   6    20     7   7    16     8   8    12     9   9     8     10 10     4     > diff(df)  error in r[i1] - r[-length(r):-(length(r) - lag + 1l)] :    non-numeric argument binary operator

can tell me why error occurs?

diff wants matrix or vector rather data frame. try

data.frame(diff(as.matrix(df)))

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