Match the feature set of a dfm to given feature names
Match the feature set of a dfm to a specified vector of feature names.
For existing features in x for which there is an exact match for an
element of features, these will be included. Any features in x
not features will be discarded, and any feature names specified in
features but not found in x will be added with all zero counts.
dfm_match(x, features)
x |
a dfm |
features |
character; the feature names to be matched in the output dfm |
Selecting on another dfm's featnames() is useful when you
have trained a model on one dfm, and need to project this onto a test set
whose features must be identical. It is also used in
bootstrap_dfm().
A dfm whose features are identical to those specified in
features.
Unlike dfm_select(), this function will add feature names
not already present in x. It also provides only fixed,
case-sensitive matches. For more flexible feature selection, see
dfm_select().
# matching a dfm to a feature vector
dfm_match(dfm(""), letters[1:5])
dfm_match(data_dfm_lbgexample, c("A", "B", "Z"))
dfm_match(data_dfm_lbgexample, c("B", "newfeat1", "A", "newfeat2"))
# matching one dfm to another
txt <- c("This is text one", "The second text", "This is text three")
(dfmat1 <- dfm(tokens(txt[1:2])))
(dfmat2 <- dfm(tokens(txt[2:3])))
(dfmat3 <- dfm_match(dfmat1, featnames(dfmat2)))
setequal(featnames(dfmat2), featnames(dfmat3))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.