让事情之间完全相同似乎很棘手nltk
and tm
关于预处理步骤,所以我认为最好的方法是使用rpy2
在 R 中运行预处理并将结果提取到 python 中:
import rpy2.robjects as ro
preproc = [x[0] for x in ro.r('''
tweets = read.csv("tweets.csv", stringsAsFactors=FALSE)
library(tm)
library(SnowballC)
corpus = Corpus(VectorSource(tweets$Tweet))
corpus = tm_map(corpus, tolower)
corpus = tm_map(corpus, removePunctuation)
corpus = tm_map(corpus, removeWords, c("apple", stopwords("english")))
corpus = tm_map(corpus, stemDocument)''')]
然后,您可以将其加载到scikit-learn
——为了让事情在两者之间匹配,你需要做的唯一一件事就是CountVectorizer
和DocumentTermMatrix
就是删除长度小于3的项:
from sklearn.feature_extraction.text import CountVectorizer
def mytokenizer(x):
return [y for y in x.split() if len(y) > 2]
# Full document-term matrix
cv = CountVectorizer(tokenizer=mytokenizer)
X = cv.fit_transform(preproc)
X
# <1181x3289 sparse matrix of type '<type 'numpy.int64'>'
# with 8980 stored elements in Compressed Sparse Column format>
# Sparse terms removed
cv2 = CountVectorizer(tokenizer=mytokenizer, min_df=0.005)
X2 = cv2.fit_transform(preproc)
X2
# <1181x309 sparse matrix of type '<type 'numpy.int64'>'
# with 4669 stored elements in Compressed Sparse Column format>
让我们验证一下它是否与 R 匹配:
tweets = read.csv("tweets.csv", stringsAsFactors=FALSE)
library(tm)
library(SnowballC)
corpus = Corpus(VectorSource(tweets$Tweet))
corpus = tm_map(corpus, tolower)
corpus = tm_map(corpus, removePunctuation)
corpus = tm_map(corpus, removeWords, c("apple", stopwords("english")))
corpus = tm_map(corpus, stemDocument)
dtm = DocumentTermMatrix(corpus)
dtm
# A document-term matrix (1181 documents, 3289 terms)
#
# Non-/sparse entries: 8980/3875329
# Sparsity : 100%
# Maximal term length: 115
# Weighting : term frequency (tf)
sparse = removeSparseTerms(dtm, 0.995)
sparse
# A document-term matrix (1181 documents, 309 terms)
#
# Non-/sparse entries: 4669/360260
# Sparsity : 99%
# Maximal term length: 20
# Weighting : term frequency (tf)
正如您所看到的,现在两种方法之间存储的元素和术语的数量完全匹配。