replace some column values from a data.frame based on another data.frame

Question

I have two data.frames, (df1, df2) and I would like to replace the values in columns P1-P10 the letters with the values of df1$V2 but keeping the first two colu

Answer 1

You can match the values of df2[3:12] in df1[[1]]. These row numbers are used to extract the values from df1[2].

df2[3:12] <- df1[match(as.character(unlist(df2[3:12])), 
                       as.character(df1[[1]])), 2]

The result (df2):

  Name bd         P1         P2         P3         P4         P5         P6         P7         P8         P9        P10
1    H  5  0.1199355  0.3752010 -0.3926061 -1.1039548 -0.1107821  0.9867373 -0.3360094 -0.7488000 -0.3926061  2.0667704
2    U  4  0.1168599  0.1168599  0.9867373  1.3521418  0.9867373 -0.3360094 -0.7724007 -0.3926061 -0.3360094 -1.2543480
3    R  3 -1.2337890 -0.1107821 -0.7724007  2.0667704  0.3752010  0.4645504  0.9867373  0.1168599 -0.0981773 -0.3926061
4    G  2 -0.3926061  0.3199261 -0.0981773 -0.1107821  2.0667704 -1.1039548 -1.2337890  0.3199261 -1.2337890 -2.1534678
5    C  6 -2.1534678 -1.1039548 -1.1039548 -0.7488000  0.4645504  0.3199261 -2.1534678 -0.3360094  0.9867373  0.8771467
6    I  1  0.6171634  0.6224091  1.8011711  0.7292998  0.8771467  2.0667704  0.3752010  0.4645504 -2.1534678 -0.7724007

If you don't want to replace the values inside df2, you can create a new data frame df4 with

df4 <- "[<-"(df2, 3:12, value = df1[match(as.character(unlist(df2[3:12])), 
                                          as.character(df1[[1]])), 2])