I have a data frame that looks like this:
Month GSI
1993.01 -0.57567056
1993.02 -1.15549239
1993.03 -1.00353071
1993.04 -0.10698880
1993.05 -0.31903591
1993.06 0.30361638
1993.07 1.24528915
1993.08 0.85104370
1993.09 1.24680092
1993.10 1.42521406
As you can see, the "Month" column is meant to be a date in the format "year.month". I would like to reformat this column to the traditional "%Y-%m" format so that the data frame looks something more like this:
Date GSI
1993-01 -0.57567056
1993-02 -1.15549239
1993-03 -1.00353071
1993-04 -0.10698880
1993-05 -0.31903591
1993-06 0.30361638
1993-07 1.24528915
1993-08 0.85104370
1993-09 1.24680092
1993-10 1.42521406
How can I go about changing the format of this column to be recognizable as a date column? Currently, the class of the "Month" column is numeric.
You can use sub, with capturing groups in the regular expression:
df$Month <- sub("^(\\d{4})\\.(\\d{2})$", "\\1-\\2", format(df$Month, 2))
df
#> Month GSI
#> 1 1993-01 -0.5756706
#> 2 1993-02 -1.1554924
#> 3 1993-03 -1.0035307
#> 4 1993-04 -0.1069888
#> 5 1993-05 -0.3190359
#> 6 1993-06 0.3036164
#> 7 1993-07 1.2452892
#> 8 1993-08 0.8510437
#> 9 1993-09 1.2468009
#> 10 1993-10 1.4252141
Input Data
df <- structure(list(Month = c(1993.01, 1993.02, 1993.03, 1993.04,
1993.05, 1993.06, 1993.07, 1993.08, 1993.09, 1993.1), GSI = c(-0.57567056,
-1.15549239, -1.00353071, -0.1069888, -0.31903591, 0.30361638,
1.24528915, 0.8510437, 1.24680092, 1.42521406)), class = "data.frame", row.names = c(NA,
-10L))
df
#> Month GSI
#> 1 1993.01 -0.5756706
#> 2 1993.02 -1.1554924
#> 3 1993.03 -1.0035307
#> 4 1993.04 -0.1069888
#> 5 1993.05 -0.3190359
#> 6 1993.06 0.3036164
#> 7 1993.07 1.2452892
#> 8 1993.08 0.8510437
#> 9 1993.09 1.2468009
#> 10 1993.10 1.4252141