dtm_align {udpipe}

Reorder a Document-Term-Matrix alongside a vector or data.frame

Description

This utility function is useful to align a Document-Term-Matrix with information in a data.frame or a vector to predict, such that both the predictive information as well as the target is available in the same order.
Matching is done based on the identifiers in the rownames of x and either the names of the y vector or the first column of y in case it is a data.frame.

Usage

dtm_align(x, y, FUN, ...)

Arguments

x

a Document-Term-Matrix of class dgCMatrix (which can be an object returned by document_term_matrix)

y

either a vector or data.frame containing something to align with x (e.g. for predictive purposes).

• In case y is a vector, it should have names which are available in the rownames of x.

• In case y is a data.frame, it's first column should contain identifiers which are available in the rownames of x.

FUN

a function to be applied on x before aligning it to y. See the examples

...

further arguments passed on to FUN

Value

a list with elements x and y containing the document term matrix x in the same order as y.

• If in y a vector was passed, the returned y element will be a vector

• If in y a data.frame was passed with more than 2 columns, the returned y element will be a data.frame

• If in y a data.frame was passed with exactly 2 columns, the returned y element will be a vector

Only returns data of x with overlapping identifiers in y.

See Also

document_term_matrix

Examples

x <- matrix(1:9, nrow = 3, dimnames = list(c("a", "b", "c")))
x
dtm_align(x = x, 
          y = c(b = 1, a = 2, c = 6, d = 6))
dtm_align(x = x, 
          y = c(b = 1, a = 2, c = 6, d = 6, d = 7, a = -1))
          
data(brussels_reviews)
data(brussels_listings)
x <- brussels_reviews
x <- strsplit.data.frame(x, term = "feedback", group = "listing_id")
x <- document_term_frequencies(x)
x <- document_term_matrix(x)
y <- brussels_listings$price
names(y) <- brussels_listings$listing_id

## align a matrix of predictors with a vector to predict
trainset <- dtm_align(x = x, y = y)
trainset <- dtm_align(x = x, y = y, FUN = function(dtm){
  dtm <- dtm_remove_lowfreq(dtm, minfreq = 5)
  dtm <- dtm_sample(dtm)
  dtm
})
head(names(y))
head(rownames(x))
head(names(trainset$y))
head(rownames(trainset$x))

## align a matrix of predictors with a data.frame
trainset <- dtm_align(x = x, y = brussels_listings[, c("listing_id", "price")])
trainset <- dtm_align(x = x, 
                y = brussels_listings[, c("listing_id", "price", "room_type")])
head(trainset$y$listing_id)
head(rownames(trainset$x))

## example with duplicate data in case of data balancing
dtm_align(x = matrix(1:30, nrow = 3, dimnames = list(c("a", "b", "c"))), 
          y = c(a = 1, a = 2, b = 3, d = 6, b = 6))
target   <- subset(brussels_listings, listing_id %in% brussels_reviews$listing_id)
target   <- rbind(target[1:3, ], target[c(2, 3), ], target[c(1, 4), ])
trainset <- dtm_align(x = x, y = target[, c("listing_id", "price")])
trainset <- dtm_align(x = x, y = setNames(target$price, target$listing_id))
names(trainset$y)
rownames(trainset$x)