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johnmackintosh/update_rdatatable_with_lapply.R

Created August 30, 2022 08:43
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how to use lapply and .SD to update columns within rdatatable
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update_rdatatable_with_lapply.R
# columns to update:
char_cols <- c("areaname", "parent_area")
# 1. convert to character, then
# 2. replace '&' with 'and'
DT[,(char_cols) := lapply(.SD, as.character), .SDcols = char_cols]
DT[,(char_cols) := lapply(.SD, gsub, pattern = ' & ', replacement = ' and '), .SDcols = char_cols]
# Or do both at once by chaining:
DT[,(char_cols) := lapply(.SD, as.character), .SDcols = char_cols
][,(char_cols) := lapply(.SD, gsub, pattern = ' & ', replacement = ' and '), .SDcols = char_cols]
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