How to add a value to a column, according to a key in R

Question

a data of annual precipitation of each year in a data frame
a data table, where are is the information of year

I need to add the information of the annual precipitation to the data table according to the year key.

data_table <- data.frame("dat" = c(2010, 2010, 2010, 2011, 2011, 2012, 2012, 2012))

prec_data <- data.frame("variable" = c(2010, 2011, 2012),
                "value" = c(500, 435, 451))

data_table$prec <- ??

Thank you for your attention and answers.

`merge(data_table, prec_data, by.x = 'dat', by.y = 'variable')` — alistaire, Feb 18 '17 at 23:26

score 1 · Accepted Answer · answered Feb 18 '17 at 23:27

1

 merge(data_table, prec_data, by.x="dat", by.y="variable")

answered Feb 18 '17 at 23:27

Bernhard

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How to add a value to a column, according to a key in R

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