如何在Pandas中创建DataFrame

Question

我正在使用playerStat.csv,其中包含8个列,我只需要2个.所以我试图创建一个只有这2列的新DataFrame.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
dataset = pd.read_csv("HLTVData/playerStats.csv")
dataset.head(20)

我只需要ADR和评级.

所以我首先用数据集创建一个矩阵.

mat = dataset.as_matrix()
#4 is the ADR and 6 is the Rating
newDAtaSet = pd.DataFrame(dataset, index=indexMatrix,columns=(mat[:,4],mat[:,6]) )

但它没有用,它抛出了一个例外

NameError                                 Traceback (most recent call last)
<ipython-input-10-1f975cc2514a> in <module>()
      1 #4 is the ADR and 6 is the Rating
----> 2 newDataSet  = pd.DataFrame(dataset, index=indexMatrix,columns=(mat[:,4],mat[:,6]) )


NameError: name 'indexMatrix' is not defined

我也尝试过使用数据集.

newDataSet = pd.DataFrame(dataset, index=np.array(range(dataset.shape[0])), columns=dataset['ADR'])

/home/tensor/miniconda3/envs/tensorflow35openvc/lib/python3.5/site-packages/pandas/core/internals.py in _make_na_block(self, placement, fill_value)
   3984 
   3985         dtype, fill_value = infer_dtype_from_scalar(fill_value)
-> 3986         block_values = np.empty(block_shape, dtype=dtype)
   3987         block_values.fill(fill_value)
   3988         return make_block(block_values, placement=placement)

MemoryError: 

Answer 1

我认为你需要参数usecols在read_csv:

dataset = pd.read_csv("HLTVData/playerStats.csv", usecols=['ADR','Rating'])

要么:

dataset = pd.read_csv("HLTVData/playerStats.csv", usecols=[4,6])