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Replace DT1.x with DT2.y when DT1.x and DT2.x are the same in R

I want to do this using data tables in R.

So I start with this

     dtMain
           Name      state
    1: CompanyC         CA
    2: CompanyM         MN
    3: CompanyC1 California
    4: CompanyT         TX

     statesFile
       stateExpan state
    1:      Texas    TX
    2:  Minnesota    MN
    3: California    CA

Where dtMain$State == statesFile$state

, I want to replace dtMain$State

with statesFile$stateExpan

and get this

      dtMain
           Name      state
    1: CompanyA California
    2: CompanyB  Minnesota
    3: CompanyC California
    4: CompanyD      Texas

Here's the code to create 2 files

library(data.table)
dtMain <- data.table(Name  = c("CompanyA"  ,"CompanyB","CompanyC","CompanyD"),
                 state = c("CA","MN","California","TX"))
statesFile <- data.table( stateExpan = c("Texas","Minnesota","California"),
                          state = c("TX","MN","CA"))

My problem is the next level of this R is searching for dataframe rows where some columns match other columns and I'm looking for a data table solution.

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1 answer


Use connection to update:

dtMain[statesFile, on=.(state), state := i.stateExpan ]


The prefix i.*

indicates that it is from table i

in x[i, on=, j]

. This is optional here.

For details see ?data.table

.

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