より少ない次元で多次元配列にアクセスするにはどうすればよいですか?

<code class="python">m, n = a.shape[1:]
I, J = np.ogrid[:m, :n]
a_max_values = a[idx, I, J]</code>

<code class="python">def argmax_to_max(arr, argmax, axis):
    new_shape = list(arr.shape)
    del new_shape[axis]
    grid = np.ogrid[tuple(map(slice, new_shape))]
    grid.insert(axis, argmax)
    return arr[tuple(grid)]</code>

<code class="python">def all_idx(idx, axis):
    grid = np.ogrid[tuple(map(slice, idx.shape))]
    grid.insert(axis, idx)
    return tuple(grid)</code>

<code class="python">a_max_values = a[all_idx(idx, axis=axis)]
b_max_values = b[all_idx(idx, axis=axis)]</code>