merge - Merging 2 dataframe tables by multiple columns in R

Question

Let's say we have 2 dataframe tables:

• dfA has col1, col2, col3, and col4
• dfB has col5, col6, and col7

if we want to join these 2 dataframe tables using merge by multiple columns( for instance, col1 can connect with col5 & col6), what's the best way to do it? I tried this:

# trying to get a left_join using merge. is that possible? 
dt = merge(dfA, dfB, x.by=c('col1','col1'), y.by=c('col5','col6'), all.x=true) 

Worked fine in python, R is throwing an error: <<Error in fix.by(by.y, y) : 'by' must specify uniquely valid columns>>

Answer 1

等待大神答复