vctrd - 4 months ago 23

R Question

I'd like to apply a function by rows on a data.frame to concatenate column titles depending on the value in the row.

`df`

A B

1 TRUE TRUE

2 FALSE TRUE

3 FALSE FALSE

A B Result

1 TRUE TRUE A / B

2 FALSE TRUE B

3 FALSE FALSE NA

I read about dplyr using mutate() and rowwise(), but I don't know how to apply them since the columns aren't constants.

for a row "i" I would do something like:

`paste(names(df)[as.logical(df[i,])], collapse = ' / ')`

Any help would be welcome.

Thank you.

Answer

We can use `apply`

with `MARGIN=1`

to loop over the rows, subset the `names`

of the vector using the logical `vector`

as index and `paste`

them together.

```
df$Result <- apply(df, 1, FUN = function(x) paste(names(x)[x], collapse=" / "))
```