广播到numpy矩阵时出错

Question

I know this is a relatively common topic on stackoverflow but I couldn't find the answer I was looking for. Basically, I am trying to make very efficient code (I have rather large data sets) to get certain columns of data from a matrix. Below is what I have so far. It gives me this error: could not broadcast input array from shape (2947,1) into shape (2947)

def get_data(self, colHeaders):
        temp = np.zeros((self.matrix_data.shape[0],len(colHeaders)))
        for col in colHeaders:
            index = self.header2matrix[col]
            temp[:,index:] = self.matrix_data[:,index]
        data = np.matrix(temp)
        return temp

Answer 1

Maybe this simple example will help:

In [70]: data=np.arange(12).reshape(3,4)
In [71]: header={'a':0,'b':1,'c':2}
In [72]: col=['c','a']
In [73]: index=[header[i] for i in col]

In [74]: index
Out[74]: [2, 0]

In [75]: data[:,index]
Out[75]: 
array([[ 2,  0],
       [ 6,  4],
       [10,  8]])

data is some sort of 2D array, header is a dictionary mapping names to column numbers. Using the input col , I construct a column index list. You can select all columns at once, rather than one by one.