Numpy错误“无法将字符串转换为float:'Illinois'”

Question

我在Google Sheets中创建了下表，并将其作为CSV文件下载。

我的代码贴在下面。我真的不知道失败在哪里。我试图突出显示并逐行运行代码，但它总是抛出那个错误。

# Data Preprocessing

# Import Libraries
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

# Import dataset
dataset = pd.read_csv('Data2.csv')
X = dataset.iloc[:, :-1].values
y = dataset.iloc[:, 5].values

# Replace Missing Values
from sklearn.preprocessing import Imputer
imputer = Imputer(missing_values = 'NaN', strategy = 'mean', axis = 0)
imputer = imputer.fit(X[:, 1:5 ])
X[:, 1:6] = imputer.transform(X[:, 1:5])

我得到的错误是：

Could not convert string to float: 'Illinois'

我的错误信息上方还有这一行

array = np.array(array, dtype=dtype, order=order, copy=copy)

我的代码似乎无法读取包含浮点数的GPA列。也许我没有正确地创建那个列，必须指定它们是浮动的？

***我正在更新完整的错误消息：

     [15]: runfile('/Users/jim/Desktop/Machine Learning Class/Part 1/Machine Learning A-Z Template Folder/Part 1 - Data Preprocessing/data_preprocessing_template2.py', wdir='/Users/jim/Desktop/Machine Learning Class/Part 1/Machine Learning A-Z Template Folder/Part 1 - Data Preprocessing')
Traceback (most recent call last):

  File "<ipython-input-15-5f895cf9ba62>", line 1, in <module>
    runfile('/Users/jim/Desktop/Machine Learning Class/Part 1/Machine Learning A-Z Template Folder/Part 1 - Data Preprocessing/data_preprocessing_template2.py', wdir='/Users/jim/Desktop/Machine Learning Class/Part 1/Machine Learning A-Z Template Folder/Part 1 - Data Preprocessing')

  File "/Users/jim/anaconda3/lib/python3.6/site-packages/spyder/utils/site/sitecustomize.py", line 710, in runfile
    execfile(filename, namespace)

  File "/Users/jim/anaconda3/lib/python3.6/site-packages/spyder/utils/site/sitecustomize.py", line 101, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "/Users/jim/Desktop/Machine Learning Class/Part 1/Machine Learning A-Z Template Folder/Part 1 - Data Preprocessing/data_preprocessing_template2.py", line 16, in <module>
    imputer = imputer.fit(X[:, 1:5 ])

  File "/Users/jim/anaconda3/lib/python3.6/site-packages/sklearn/preprocessing/imputation.py", line 155, in fit
    force_all_finite=False)

  File "/Users/jim/anaconda3/lib/python3.6/site-packages/sklearn/utils/validation.py", line 433, in check_array
    array = np.array(array, dtype=dtype, order=order, copy=copy)

ValueError: could not convert string to float: 'Illinois'