Returns document subsets of a dfm that meet certain conditions,
including direct logical operations on docvars (document-level variables).
dfm_subset functions identically to
using non-standard evaluation to evaluate conditions based on the
docvars in the dfm.
dfm object to be subsetted
logical expression indicating the documents to keep: missing values are taken as false
expression, indicating the docvars to select from the dfm; or a dfm object, in which case the returned dfm will contain the same documents as the original dfm, even if these are empty. See Details.
To select or subset features, see
select is a dfm, then the returned dfm will be equal in
document dimension and order to the dfm used for selection. This is the
document-level version of using
pattern is a dfm: that function matches features, while
dfm_subset will match documents.
dfm object, with a subset of documents (and docvars) selected according to arguments
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corp <- corpus(c(d1 = "a b c d", d2 = "a a b e", d3 = "b b c e", d4 = "e e f a b"), docvars = data.frame(grp = c(1, 1, 2, 3))) dfmat <- dfm(corp) # selecting on a docvars condition dfm_subset(dfmat, grp > 1) # selecting on a supplied vector dfm_subset(dfmat, c(TRUE, FALSE, TRUE, FALSE)) # selecting on a dfm dfmat1 <- dfm(c(d1 = "a b b c", d2 = "b b c d")) dfmat2 <- dfm(c(d1 = "x y z", d2 = "a b c c d", d3 = "x x x")) dfm_subset(dfmat1, subset = dfmat2) dfm_subset(dfmat1, subset = dfmat2[c(3,1,2), ])
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