英文:
How to add column to df with zero array
问题
我想要将一个新的大小为20 x 20的零数组列添加到现有的数据框中。
我尝试过以下代码：
df['matrix'] = np.zeros((20, 20))
但收到了错误信息：
ValueError: Length of values (20) does not match length of index (26651)
看起来它试图将一个单独的零矩阵附加到该列，而不是使每个条目在新列中都是零矩阵。
如果我没有正确格式化问题，对此不熟悉，我深感抱歉。
英文:
I would like to add a new column of zero arrays size 20 x 20 to an existing df.
I tried
df['matrix']= np.zeros((20,20))
received error
ValueError: Length of values (20) does not match length of index (26651)
It seems like it is trying to append a single zero matrix to the column as opposed to having each entry in a new column be a zero matrix.
Apologies if I didn't format the question correctly, I am new to this site.
答案1
得分: 0
Pandas尝试广播numpy数组以适应数据框，但在这种情况下并不有用。
为了避免这种情况，您可以制作一个数组列表。
df["matrix"] = [np.zeros((20, 20)) for _ in df.index]
或者使用apply来获取每个单元格中所需的值。
df["matrix"] = df.apply(lambda _: np.zeros((20, 20)), axis=1)
英文:
Pandas tries to broadcast the numpy array to fit your dataframe in ways that are not helpful in this case.
To avoid this you could make a list of the arrays.
df["matrix"] = [np.zeros((20,20)) for _ in df.index]
Or use apply to get the value you want in each cell
df["matrix"] = df.apply(lambda _: np.zeros((20, 20)), axis=1)
答案2
得分: 0
如果您想要单独的一列，我建议添加一个包含所需信息的 pd.Series，例如：
df['matrix'] = [[0]*20] * len(df)
英文:
If you want a single column I would suggest adding a pd.Series with the desired information, such as:
df['matrix'] = [[0]*20] * len(df)
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