如何找到最后一个非空元素的索引单元阵列 [英] How to find index of the last non-empty element in a cell array

问题描述

我初始化了一个很长的电池阵列（矢量？）

I initialized a very long cell array(vector?)

train_labels = cell(16218, 1);

这将使用来自50个不同的文件夹中的文件，以确保文件是在正确的位置索引，我需要被写入到最后一个单元格数组的索引进行填充。

These will be populated using files from 50 different folders, to make sure that the files are indexed in the right location, I need the index of the last cell array that was written to.

例如读取一个文件夹，在 train_labels 该指数曾达到后 5406 。我们了解，他们必须保存到是下一个索引下一个文件夹读取图像 5407 。为了使这项工作，我需要找到的最后一个非空数组的位置 train_labels 。

For example after reading one folder, the index in train_labels had reached 5406. Now to read the images from the next folder they must be saved to the next index that is 5407. To make that work I need to find the location of the last non-empty array in train_labels.

由于简单的找到（train_labels，1，'最后'）不会对电池阵列工作。我用 cellfun 但是这也不能正常工作。这是我尝试：

Since the simple find(train_labels,1,'last') does not work on cell arrays. I used cellfun but that is also not working. This is what I tried:

cellfun(@find, train_labels, 'last')
Error using cellfun
Input #3 expected to be a cell array, was char instead.

请问AP preciate如何获取单元阵列的最后一个索引任何指导。

Would appreciate any guidance on how to get the last index of the cell array.

感谢您

推荐答案

使用 cellfun 与'的isEmpty 选项 -

last_non_empty_index = find(~cellfun('isempty',train_labels),1,'last')

您也可以使用 cellfun（@isempty ..），但我相信一定是慢。这较详细的无证MATLAB博客帖子进行了讨论。

You can also use cellfun(@isempty..), but I believe that must be slower. This has been discussed in detail in this Undocumented MATLAB Blog post.

的isEmpty 是内置的，因此似乎是一个优化的实现。其他内置插件，在 cellfun 的2014A版本都可以是 - 伊斯雷尔， ISLOGICAL，长度，为ndims ，'prodofsize ，'大小'，'isclass 。我希望，这些都是快速的实现也是如此。这些详细信息都在其官方文档中有可与＆GT进行访问;＆GT;帮助cellfun 。

isempty is a built-in and as such appears to be an optimized implementation. Other built-ins that are available in 2014A version of cellfun are - 'isreal', 'islogical', 'length', 'ndims', 'prodofsize', 'size', 'isclass'. I am hoping that these are fast implementations as well. More info on these are available in its official documentation that can be accessed with >> help cellfun.

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