How to update selected rows of spatial data frame in R

Question

I have a SpatialPointsDataFrame read via rgdal::readOGR

require(rgdal)
my_sp_layer <- readOGR(dsn="my_dsn", layer="my_layer_file")

# select rows using col_attrib column
my_sp_layer@data[my_sp_layer@data$col_attrib == 'some value',]  

How can I update the values of the selected rows?

If it is a data.table, I would just use

my_data_table[col_attrib == 'some value', col_to_update := 'new value']

Answer 1

First convert the column you want to amend to character as this will be set to factor by default:

shapefile@data$column_update <- as.character(shapefile@data$column_update)

Then just select the column you want to update with subset notation ([ ]) and use assign <-:

Shapefile@data$column_update[shapefile@data$column_condition == "condition"] <- " new_value"