fcm() objects created with the default of tri = TRUE produce misleading feature frequencies when using topfeatures(), which calls the inherited method for dfm objects that simply sums the columns. This down weights features that occur first.
library("quanteda")
## Package version: 3.1.0
## Unicode version: 13.0
## ICU version: 69.1
## Parallel computing: 12 of 12 threads used.
## See https://quanteda.io for tutorials and examples.
txt <- c(
"a b c d",
"a a b c d",
"c d"
)
dfmat <- tokens(txt, remove_punct = TRUE) %>%
dfm()
fcmat <- fcm(dfmat)
fcmat
## Feature co-occurrence matrix of: 4 by 4 features.
## features
## features a b c d
## a 1 3 3 3
## b 0 0 2 2
## c 0 0 0 3
## d 0 0 0 0
topfeatures(fcmat)
## d c b a
## 8 5 3 1A solution would be to create a new method fcm.topfeatures() that first forces the matrix to be symmetric and then sums the columns.
topfeatures.fcm <- function(x,
n = 10,
decreasing = TRUE,
scheme = c("count", "docfreq"),
...) {
topfeatures(as.dfm(Matrix::forceSymmetric(x)))
}
topfeatures.fcm(fcmat)
## a c d b
## 10 8 8 7
fcm()objects created with the default oftri = TRUEproduce misleading feature frequencies when usingtopfeatures(), which calls the inherited method for dfm objects that simply sums the columns. This down weights features that occur first.A solution would be to create a new method
fcm.topfeatures()that first forces the matrix to be symmetric and then sums the columns.