零维numpy.ndarray:唯一的元素是2D数组:如何访问它? [英] Zero-dimensional numpy.ndarray : only element is a 2D array : how to access it?

问题描述

我已经使用scipy.io导入了Matlab * .mat文件，并尝试从中提取2D数据.里面有几个数组，当我尝试获取它们时，我陷入了最后的操作.

I have imported a Matlab *.mat file using scipy.io and trying to extract the 2D data from it. There are several arrays inside, and when I am trying to get them I got stuck at the last operation.

数据如下图所示.当我尝试建立索引时: IndexError:数组的索引过多

The data looks like the image below. When I try to index it: IndexError: too many indices for array

我已经搜索到看起来像一个单值元组，其中唯一的元素是我的数组.原则上，这必须是可索引的，但不起作用. type(data)返回< class'numpy.ndarray'>

I have googled to the point that it looks like a single valued tuple, where the only element is my array. This in principle must be indexable, but it doesn't work. The type(data) returns <class 'numpy.ndarray'>

问题是:如何从这种数据结构中提取2D阵列?

So the question is: how do I get my 2D array out of this data structure?

    data[0] # Doesn't work.

推荐答案

在 loadmat 上进行搜索应会产生许多SO问题，以帮助您区分该结果. loadmat 必须将MATLAB对象转换为Python/numpy近似值.

A search on loadmat should yield many SO questions that will help you pick apart this result. loadmat has to translate MATLAB objects into Python/numpy approximations.

data = io.loadmat(filename)

应该产生一个带有一些封面键和各种数据键的字典. list(data.keys())进行识别.

should produce a dictionary with some cover keys and various data keys. list(data.keys()) to identify those.

x = data['x']

应与MATLAB工作区中的 x 变量匹配.可以是二维的F数组，对应于MATLAB矩阵.

should match the x variable in the MATLAB workspace. It could be a 2d, order F array, corresponding to a MATLAB matrix.

可能是(n，m)个对象dtype数组，对应于MATLAB单元格.

It could be (n,m) object dtype array, corresponding to a MATLAB cell.

它可以是结构化的数组，其中字段名称对应于MATLAB的 struct 属性.

It could be a structured array, where the field names correspond to a MATLAB struct attributes.

在您的情况下，看起来您有一个0d对象dtype数组.形状是()，一个空的元组(1d具有(n，)形状，2d具有(n，m)形状，等等).您可以使用以下方法将元素从()数组中拉出:

In your case it looks like you have a 0d object dtype array. The shape is (), an empty tuple (1d has (n,) shape, 2d has (n,m) shape, etc). You can pull the element out of a () array with:

 y[()]
 y.item()

[()] 看起来很奇怪，但这是合乎逻辑的.对于一维数组， y [1] 可以写为 y [(1，)] .对于2d， y [1,2] 和 y [(1,2)] 是相同的.标引元组应与维数匹配.因此，()可以索引()形状数组.

The [()] looks odd, but it's logical. For a 1d array y[1] can be written as y[(1,)]. For 2d, y[1,2] and y[(1,2)] are the same. The indexing tuple should match the number of dimensions. Hence a () can index a () shape array.

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