How to manually construct or modify a cross-validation object in MATLAB?

6 次查看（过去 30 天）
Vilmantas Gegzna
Vilmantas Gegzna 2015-4-14
评论： Alex Ryabov 2024-5-30
Short question:
I want your help to manually construct or modify Matlab cross-validation (CV) object created using function cvpartition when it's known which observations belong to training and which to validation partitions.
Extended question:
I have a kind of specific dataset in which several observations (each represented by a separate row) belong to the same object of investigation (e.g. measurements of the same object were performed several times). Each object (and it's observation) belongs to a certain class (e.g. yellow object, green object, etc.) as well. The problem is this: it's needed a CV object in which all observations of the same object belong to the same (either training or validation) partition as a block of data (unfortunately I'm not sure how to implement this) and the data would be distributed to partitions in stratified way (luckily, this is implemented in function cvpartition). I tried to access indices of CV object (cvo.indices) but they are locked. Here cvo is:
cvType = 'kfold';
nPartitions = 5;
cvo = cvpartition(my_classes,cvType,nPartitions);
Your insights and ideas how to construct or modify cvo manually are welcomed.
  2 个评论
Jan
Jan 2018-12-20
[MOVED from flags] Flagged as Unclear by James Ratti on 19 Oct 2018.
This solution no longer works - was there a concurrent patch that provided a workaround?
@James: This is the question. Which solution do you mean?
Rik
Rik 2021-3-29
Ran in:
Comment posted as flag by patrck rich:
the solution is no longer working in recent versions
That is always a risk when trying to modify internal files. However, I ran the lines below in the online interface (I cleared the output, as I don't expect Mathworks would be happy with me sharing their files..)
%type(which('cvpartition'))
OS={'Windows','macOS','Linux'};fprintf('This is version %s, running on %s.',version,OS{[ispc ismac isunix&&~ismac]})
This is version 9.10.0.1613233 (R2021a), running on Linux.
As far as I can judge from the code I can read, I don't see a reason why it wouldn't still work, but feel free to post a comment explaining which exact steps you took and which lines you modified.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Vilmantas Gegzna
Vilmantas Gegzna 2015-4-22
编辑：Vilmantas Gegzna 2015-4-22
I found, that I can modify the cross-validation object (CVO) which class is cvpartition by modifying several lines in cvpartition.m file from:
properties(GetAccess = 'private', SetAccess = 'private')
to:
properties(GetAccess = 'public', SetAccess = 'public')
This allowed me to modify indices of CVO manually.
I wonder if there are any other way to set indices of CVO without changing the lines in cvpartition.m? This is the case when I want to run Matlab on my campus computer.
  2 个评论
RZM
RZM 2018-7-6
I cannot change the properties, it pops up an error message that Access is denied!
Sergio Gutierrez
Sergio Gutierrez 2018-8-11
I have done the same modification as Albert Sama said in the below comment. You require administrative rights to make changes. I used Notepad++ in administrator mode.

请先登录，再进行评论。

更多回答（3 个）

Jo
Jo 2016-11-4
Hi,
It seems that one year later your solution is not working anymore, maybe they changed the function.
Indeed, I tried to modify as you suggested "properties(GetAccess = 'public', SetAccess = 'public')", but it only allows me to access to the number of observations and not the indices. Indices are created by "methods" defined in cvpartition.m (test, training). And I do not understand how to change these to choose my own indices.
Maybe if you have progessed in all that since you first posted your question.... I would be really greatful to have some help in there.
Using random crossvalidation is of none interest for me, I need to choose the block myself to have a more robust solution. Thanks to anyone that can help me!!!
  3 个评论
显示 1更早的评论
Alex Ryabov
Alex Ryabov 2024-5-30
This solution works for me also, maltab 2023a.
In windows I had to run Notepad as admin to be able to edit the file

请先登录，再进行评论。

Roberto Herrera-Lara
try to do this https://chrisjmccormick.wordpress.com/2013/07/31/k-fold-cross-validation-with-matlab-code/
  1 个评论
Vilmantas Gegzna
Vilmantas Gegzna 2015-4-22
编辑：Vilmantas Gegzna 2015-4-22
Thank you, Roberto, your link provided an extremely good description of k-fold cross-validation and updated my knowledge. Unfortunately, I was searching for a bit different thing.

请先登录，再进行评论。

John Smith
John Smith 2018-11-21
Two small additions:
1.You need to update the toolbox cache https://www.mathworks.com/help/matlab/matlab_env/toolbox-path-caching-in-the-matlab-program.html
2.Restart Matlab after that

类别

在 Help Center 和 File Exchange 中查找有关 Resampling Techniques 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by