Quanteda：具有预定义功能集的文档功能矩阵

Question

我使用quanteda构建两个文档特征矩阵：

library(quanteda)
DFM1 <- dfm("this is a rock")
#        features
# docs    this is a rock
#   text1    1  1 1    1
DFM2 <- dfm("this is music")
#        features
# docs    this is music
#   text1    1  1     1

但是，我希望DFM2具有一组特定功能，即来自DFM1的功能：

DFM2 <- dfm("this is music", *magicargument* = featnames(DFM1))
#        features
# docs    this is a rock
#   text1    1  1 0    0

我缺少一个神奇的论据吗？或者是否有另一种有效的方法可以为大量的单词取代它？

Answer 1

魔术参数是pattern，您可以在其中提供其功能将匹配的dfm（包括不在目标dfm中的功能的零）：

dfm_select(DFM2, pattern = DFM1)
# Document-feature matrix of: 1 document, 4 features (50% sparse).
# 1 x 4 sparse Matrix of class "dfmSparse"
#        features
# docs    this is a rock
#   text1    1  1 0    0