[Solved] How do I compare mathematical operations between values in two columns of an R data frame based on their position?

by


We get the index of column names that start with ‘pd’ (nm1). Loop through those columns with lapply, match each column with the ‘nom’ column to get the row index. Using ifelse, we change the NA elements with the column values and the rest of the values from the ‘ID’ column.

nm1 <- grep('^pd', names(df1))
df1[nm1] <- lapply(df1[nm1], function(x) {
      i1 <- match(x, df1[['nom']])
       ifelse(is.na(i1), x, df1$ID[i1])})

data

df1 <- structure(list(ID = c(10L, 5L, 7L), nom = c("A10", 
 "A10C", "BC1"
), pd1 = c("A10C", "BCN", "hmn"), pd2 = c("BC1", "hJK", "hJj"
), pd3 = c("tt12", "LMK", "jkl")), .Names = c("ID", "nom", "pd1", 
"pd2", "pd3"), class = "data.frame", row.names = c(NA, -3L))

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solved How do I compare mathematical operations between values in two columns of an R data frame based on their position?