[英]Concatenating 2 dimensional numpy arrays in Python
I want to concatenate these two arrays我想连接这两个 arrays
a = np.array([[1,2,3],[3,4,5],[6,7,8]])
b = np.array([9,10,11])
such that这样
a = [[1,2,3,9],[3,4,5,10],[6,7,8,11]]
Tried using concatenate尝试使用连接
for i in range(len(a)):
a[i] = np.concatenate(a[i],[b[i]])
Got an error:出现错误:
TypeError: 'list' object cannot be interpreted as an integer
Tried using append尝试使用 append
for i in range(len(a)):
a[i] = np.append(a[i],b[i])
Got another error:得到另一个错误:
ValueError: could not broadcast input array from shape (4,) into shape (3,)
(New to stackoverflow, sorry if I didn't format this well) (stackoverflow 的新手,抱歉,如果我没有很好地格式化这个)
You can use hstack
and vector broadcasting for that:您可以为此使用hstack
和矢量广播:
a = np.array([[1,2,3],[3,4,5],[6,7,8]])
b = np.array([9,10,11])
res = np.hstack((a, b[:,None]))
print(res)
Output: Output:
[[ 1 2 3 9]
[ 3 4 5 10]
[ 6 7 8 11]]
Note that you cannot use concatenate
because the array have different shapes .请注意,您不能使用concatenate
,因为数组具有不同的形状。 hstack
stack horizontally the multi-dimentional arrays so it just add a new line at the end here. hstack
将多维arrays 水平堆叠,所以它只是在此处的末尾添加一个新行。 A broadcast operation ( b[:,None]
) is needed so that the appended vector is a vertical one.需要广播操作( b[:,None]
),以便附加向量是垂直向量。
You can do it like this:你可以这样做:
np.append(a,b.reshape(-1,1),axis=1)
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