data.table-提取所有文本功能

Question

As part of a function, I am trying to isolate all features that are either character or factor . My data set is a data.table .

text_features <- c(names(data_set[sapply(data_set, is.character)]), names(data_set[sapply(data_set, is.factor)]))

When I run the function I am getting an exception message that says :

Error in [.data.table (data_set, sapply(data_set, is.character)) : i evaluates to a logical vector length 87 but there are 12992 rows. Recycling of logical i is no longer allowed as it hides more bugs than is worth the rare convenience. Explicitly use rep(...,length=.N) if you really need to recycle.

I understand this error is thrown by a recent version of data.table - How should I change my code to work the same way in order to avoid this error?

Note:

packageVersion("data.table")
[1] ‘1.10.4.3’

Thanks

Answer 1

The error that you are getting is because you have commas in the wrong place when you are subsetting your inner data.tables. You want a subset of the columns, not rows:

data_set[sapply(data_set, is.character)] # subsetting rows
data_set[,sapply(data_set, is.character), with = FALSE] # subsetting columns

All that said, I think a much cleaner solution would be:

text_cols <- names(data_set)[sapply(data_set, class) %in% c("character","factor")]
data_set[, ..text_cols] # subset data