merging 2 columns followed by making a new column in a data.frame in R

Question

I want to ask, how can I make a new column in a data.frame in R by merging 2 columns (with categorical values) with all rows in the file. Following example is showing alternate categorical conditions in column_1 and column_2 how could I make column_3 by merging columns_1 and column_2? Moreover, in 4th row both columns have values, so in this case what would be in column_3. (NA are blanks).

Column_1 Column_2  Column_3
1          NA
NA          2
2           NA
NA          1
1           2

`dplyr::coalesce(df$Column_1, df$Column_2)`, or reverse the order if you want `Column_2` to take precedence — alistaire, Oct 10 '16 at 23:01
*You* have to decide what to do if both columns have values. — mathematical.coffee, Oct 10 '16 at 23:01
What do you mean by merging? Just have both values in sequence or adding up? — Daniel Winkler, Oct 10 '16 at 23:01
Don't attach your data as an image. It makes the question harder to read and is not reproducible [I've rolled it back]. — mathematical.coffee, Oct 10 '16 at 23:05

score 0 · Answer 1 · edited May 23 '17 at 10:32

Welcome to StackOverflow! Please consider providing a reproducible example to make it easier for us to help you. E.g.

df <- data.frame(Column_1 = c(1, NA, 2, NA, 1), Column_2=c(NA, 2, NA, 1, 2))

You could use ifelse here if you just wanted to stick to base R.

df$Column_3 = ifelse(is.na(df$Column_1), df$Column_2,
                     ifelse(is.na(df$Column_2), df$Column_1,
                            df$Column_1))

This says "if Column 1 is NA, use column 2. Otherwise, if Column 2 is NA, use column 1. Otherwise (both are not NA), use Column 1".

You need to decide what you want to do if both columns are not-NA.

If you want to skip some typing (of df$) you can use with

df$Column_3 = with(df,
                   ifelse(is.na(Column_1), Column_2,
                          ifelse(is.na(Column_2), Column_1,
                                 Column_1)))

merging 2 columns followed by making a new column in a data.frame in R

1 Answers1