CODEWITHSUNDEEP
rmerge
user2165857
user2165857

Reputation: 2690

R add Column to dataframe based on previous column if present

I would like to add a column to a dataframe based on a value in a second dataframe. However, if the column is not present in the second dataframe I would like to add a default value. For example, if my second dataframe contains 

> dataframe2$contents
[1] A A C A C T

I am merging on a common "id" column using:

Merged <- merge(dataframe1, dataframe2, by="id") 
# I actually only need the contents column from dataframe2

This works great however, in some cases when merging the tables there will be no "contents" column in dataframe2. If that's the case I still want a contents column, but I want to fill it with "G".

Upvotes: 1

Views: 134

Answers (1)

zx8754
zx8754

Reputation: 56219

Try this:

if(is.na(match("contents",colnames(Merged)))) Merged$contents<-"G"

If after merging there is no column named contents then add column with default value "G".

Upvotes: 1

Related Questions