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ibarraespinosa/dt.R

Created January 7, 2019 09:31
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dt.R
DT <- data.table(A = letters[c(2, 1, 2, 3, 1, 2, 3)],
B = c(5, 4, 1, 9, 8, 8, 6),
C = 6:12,
key = "A,B")
# Se puede etear los KEYS en la definicion de DT
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ibarraespinosa commented Jan 7, 2019 •
edited 

# Keyed data.table DT
DT <- data.table(A = letters[c(2, 1, 2, 3, 1, 2, 3)], 
                 B = c(5, 4, 1, 9, 8, 8, 6), 
                 C = 6:12, 
                 key = "A,B")

# Print the sequence (-2):10 for the "b" group
DT[.("b", (-2):10)]

# Add code: carry the prevailing values forwards
DT[.("b", (-2):10), roll = TRUE]

# Add code: carry the first observation backwards
DT[.("b", (-2):10), roll = TRUE, rollends = TRUE]
DT[.("b", (-2):10), roll = TRUE, rollends = c(TRUE, TRUE)] # also OK

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