pandas 更改熊猫数据框中一列的值
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Change values of one column in pandas dataframe
提问by Sparkan
How can I change the values of the column 4 to 1 and -1, so that Iris-setosa is replace with 1 and Iris-virginica replaced with -1?
如何将第 4 列的值更改为 1 和 -1，以便将 Iris-setosa 替换为 1，将 Iris-virginica 替换为 -1？
0 1 2 3 4
0 5.1 3.5 1.4 0.2 Iris-setosa
1 4.9 3.0 1.4 0.2 Iris-setosa
2 4.7 3.2 1.3 0.2 Iris-setosa
3 4.6 3.1 1.5 0.2 Iris-setosa
4 5.0 3.6 1.4 0.2 Iris-setosa
5 5.4 3.9 1.7 0.4 Iris-setosa
6 4.6 3.4 1.4 0.3 Iris-setosa
.. ... ... ... ... ...
120 6.9 3.2 5.7 2.3 Iris-virginica
121 5.6 2.8 4.9 2.0 Iris-virginica
122 7.7 2.8 6.7 2.0 Iris-virginica
123 6.3 2.7 4.9 1.8 Iris-virginica
124 6.7 3.3 5.7 2.1 Iris-virginica
125 7.2 3.2 6.0 1.8 Iris-virginica
126 6.2 2.8 4.8 1.8 Iris-virginica
I would appreciate the help.
我将不胜感激。
采纳答案by WNG
df.iloc[df["4"]=="Iris-setosa","4"]=1
df.iloc[df["4"]=="Iris-virginica","4"]=-1
回答by Vaishali
You can use replace
您可以使用替换
d = {'Iris-setosa': 1, 'Iris-virginica': -1}
df['4'].replace(d,inplace = True)
0 1 2 3 4
0 5.1 3.5 1.4 0.2 1
1 4.9 3.0 1.4 0.2 1
2 4.7 3.2 1.3 0.2 1
3 4.6 3.1 1.5 0.2 1
4 5.0 3.6 1.4 0.2 1
5 5.4 3.9 1.7 0.4 1
6 4.6 3.4 1.4 0.3 1
.. ... ... ... ... ...
120 6.9 3.2 5.7 2.3 -1
121 5.6 2.8 4.9 2.0 -1
122 7.7 2.8 6.7 2.0 -1
123 6.3 2.7 4.9 1.8 -1
124 6.7 3.3 5.7 2.1 -1
125 7.2 3.2 6.0 1.8 -1
126 6.2 2.8 4.8 1.8 -1
回答by Shiva Kishore
I would do something like this
我会做这样的事情
def encode_row(self, row):
if row[4] == "Iris-setosa":
return 1
return -1
df_test[4] = df_test.apply(lambda row : self.encode_row(row), axis=1)
df_test[4] = df_test.apply(lambda row : self.encode_row(row), axis=1)
assuming that df_testis your data frame
假设这df_test是您的数据框
回答by fuglede
Sounds like
听起来好像
df['4'] = np.where(df['4'] == 'Iris-setosa', 1, -1)
should do the job
应该做这份工作
