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rsortingmerge

How to prevent merge from reordering columns

In the following example

x <- data.frame(code = 7:9, food = c('banana', 'apple', 'popcorn'))
y <- data.frame(food = c('banana', 'apple', 'popcorn'),
                isfruit = c('fruit', 'fruit', 'not fruit'))

I would like to do x <- merge(x, y), but the problem is that merge() reorders the columns so that the by column (food) comes first. How can I prevent this and have merge(x, y) use the same column order of x and just insert the new variable (isFruit) as the third column (i.e., "code, food, isFruit" instead of "food, code, isFruit")?

I've tried this, to no avail:

merge(x, y, sort = F)

My workaround is to do this afterward

x <- x[c(2, 1, 3)]
Solution

  • Here's a generic version of your base workaround:

    merge(x, y)[, union(names(x), names(y))]