如何添加列并保存在文本文件稀疏矩阵中？答案

【问题标题】：how to add a column and save in a text file sparse matrix?如何添加列并保存在文本文件稀疏矩阵中？
【发布时间】：2016-03-09 01:35:29
【问题描述】：

TfidfVectorizer 在输出时返回稀疏矩阵，可以很容易地将其转换为 SparseDataFrame（不是常规的）。但我不知道如何向其中添加列并保存在 csv 文件中。

import pandas as pd
import numpy as np
from sklearn.feature_extraction.text import TfidfVectorizer

def get_features(data, train=False):
    tfv = TfidfVectorizer()
    if train:
        features = tfv.fit_transform(data["text"])
    else:
        features = tfv.transform(data["text"])

    features_pd = pd.SparseDataFrame([ pd.SparseSeries(features[i].toarray().ravel())
                                 for i in np.arange(features.shape[0]) ], columns = tfv.get_feature_names() )
# the next 2 lines in replacement of the previous result in empty (commas only) output  
#    features_pd = pd.DataFrame([ pd.Series(features[i].toarray().ravel())
#                                 for i in np.arange(features.shape[0]) ], columns = tfv.get_feature_names() )
# the next line results in TypeError: ufunc 'isnan' not supported for the input types ...   
   # features_pd['_class_'] = pd.SparseSeries(data["class"])

    print "F:",features_pd.iloc[[0]]
    return features_pd

if __name__ == '__main__':

    train = pd.read_csv('train.csv', header=None, names = ["class", "text"]).fillna("")
    features = get_features(train, train=True)
    features.to_csv('out.csv', index=False)

【问题讨论】：

标签： python pandas scikit-learn

【解决方案1】：

可以将稀疏矩阵转换为数组，然后可以使用常规数据框执行所有操作要进行的更改的核心：features.toarray()

features_pd = pd.DataFrame(data=features.toarray(),
                           columns = tfv.get_feature_names() )

features_pd['_class_'] = pd.Series(data["class"], index = features_pd.index)

【讨论】：