PONE-D-24-16516Research on Feature Selection for AC Contactor Vibration Signals Based on Regularized Random Forest with Recursive SelectionPLOS ONE

Dear Dr. Qi,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Aug 18 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Caio Bezerra Souto Maior, Ph.D.

Academic Editor

PLOS ONE

Journal Requirements:

1. When submitting your revision, we need you to address these additional requirements.

Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at 

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and 

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf"

2. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match. 

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

3. Thank you for stating the following financial disclosure: "This work was supported by National Natural Science Foundation of China (No. 51977132); Liaoning Science and Technology Major Project (2020JH1/10100012); Shenyang Young and Middle-aged Science and Technology Innovation Talent Program (RC210354)".

Please state what role the funders took in the study.  If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

4. Thank you for stating the following in the Acknowledgments Section of your manuscript: "This work was supported by National Natural Science Foundation of China (No. 51977132); 

Liaoning Science and Technology Major Project (2020JH1/10100012); Shenyang Young and Middleaged Science and Technology Innovation Talent Program (RC210354)".

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: "This work was supported by National Natural Science Foundation of China (No. 51977132); Liaoning Science and Technology Major Project (2020JH1/10100012); Shenyang Young and Middle-aged Science and Technology Innovation Talent Program (RC210354)."

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

5. In the online submission form, you indicated that "Due to the privacy nature of the data, it cannot be made publicly available. However, the data can be accessed by any interested party upon request to the corresponding author. Please contact qixinzhi_1999@163.com for further information regarding data access."

All PLOS journals now require all data underlying the findings described in their manuscript to be freely available to other researchers, either 1. In a public repository, 2. Within the manuscript itself, or 3. Uploaded as supplementary information.

This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If your data cannot be made publicly available for ethical or legal reasons (e.g., public availability would compromise patient privacy), please explain your reasons on resubmission and your exemption request will be escalated for approval.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The paper introduces an approach for feature selection using a regularized random forest and a recursive selection procedure, but with the traditional regularization term being modified to include the ratio of importance, relative to the maximum importance among all features, of a certain feature in the penalization. A total of 7 time-domain and 10 frequency-domain features are analyzed and selected, via both traditional feature selection methods and the proposed one, and then evaluated using four classifiers. The paper’s results show some advantage of the proposed method over other traditional feature selection methods. Some comments:

1) Review of acronyms’ definitions along all paper. Many acronyms are defined multiple times, which is not correct. For example, the “(RFRS)” acronym definition appears in the abstract, in the keywords, in the last paragraph of the introduction and then twice in the Conclusion section. Other acronyms are also defined multiple times, such as “(RF)”. Please revise those acronyms over the entire paper and only define them the first time they appear.

2) 3.3.1 Feature Extraction: pages 8-9 include the name, description and formula of multiple features, organized per paragraph. This information would be better suited in a table with three columns: name, description and formula.

3) Sections 3.3.1 and 3.3.2 have the same name “Feature Extraction”. I also believe section 3.3.2 is related to experiment and/or some sort of data processing, not Feature Extraction itself, so this name does not seem not suitable unless extra information is provided in the section’s title.

4) Section 3.3.2 Feature Extraction: in the last paragraph of page 9, Stage I is stated as # of operations ranging from 10000 to 30000 and Stage II from 30000 to 70000. In the first paragraph of page 10, Stages I and II are stated as from 10000 to 40000 and 40000 to 70000 instead. Which one is the correct value? The first time (page 9) the stages are cited must be adjusted to the correct value, while the second time (page 10) should not include the parenthesis part after ‘Stage X’ as the range for each stage was already described in the previous paragraph.

5) Fig 8: I believe this graph is relative to the three Stages described in section 3.3.2, but its legend uses the term ‘Phase X’ instead, mentioned nowhere in the paper. Either describe the term along the paper, if it is supposed to be Phase, or change it to ‘Stage X’ instead.

6) Table 4 includes the metrics Recall, F1-Score and Precision for the four feature selection methods analyzed and for four different classifiers. Accuracy should also be included in the table. Although generic and misleading in some cases, it is still an easy-to-interpret metric that, alongside the others already provided by the authors, helps understanding the advantages of the proposed approach.

7) 4.3 Results and Analysis: some more robust classifiers could be evaluated, such as MLP and a traditional Random Forest classifier.

8) 5. Conclusion: the last sentence of topic (3) is almost the same as the sentence that appears in the last paragraph of Conclusion section. Topic (3) is described by the authors as a ‘future steps’ guideline, therefore the sentence “In summary, the RFRS-based feature selection…” does not fit there. Also, future steps were not correctly defined: “exploration of new feature extraction techniques”, an example of such new techniques could be added. Also, testing your proposed methodology in different AC contactors’ datasets is an important future step and could be added in this topic.

Reviewer #2: The paper introduces a feature selection strategy based on Regularized Random Forest with Recursive Selection applied to vibration signals of AC contactors to enhance the accuracy of their condition identification. The topic is interesting and worth investigating. However, I suggest the following revision points before the paper is considered for publishing.

1) In the abstract, there is no contextualization of the problem. Why is this development worth investigating?

2) In the abstract, what is the contribution of the paper?

3) In the introduction, please consider reformulating or removing the phrase “It is known from statistical knowledge that the standard deviation is closely related to variance” given that “standard deviation is the square root of the variance”.

4) In the introduction, “[19-27]” avoid using nested citation.

5) In equation (1), what is wr and wl? Please define all terms in all equations.

6) Fig. 2 is not cited in the text.

7) Regarding the figure order, I suggest introducing and citing the figure, inserting the figure in the manuscript and then discussing it. Normally, the figures appear with any discussion.

8) Fig. 3 and its font are small, please increase it to improve readability.

9) Fig. 4 and its font are small, please increase it to improve readability.

10) In Section 3.2, few details are given about the vibration time series. It should be provided and discussed the sampling frequency in Hz, the length of the time waveform, etc? Was the vibration measurement triggered with the AC contactor movement? Each measurement contains how many openings and closings of the contactor?

11) In Table 1, It is not clear if the information presented refers to the accelerometer, contactor or experiment. Please clarify it in the table and text.

12) Avoid using “frequency time waveform”, I suggest using frequency spectrum instead.

13) In equation (22), “fi refers to the frequency-domain value” explain it better.

14) In Section 4.1, how training and testing datasets are selected? How many contactors have been used? How long did it take to carry out measurements? How many hours/days of experiment have been carried out? What has been done to avoid overfit of the models? What are the results during training and testing? How many samples have been considered in the training and testing datasets?

15) I understood that four methods have been used to compare the results: RFRS, Spearman's Rho, Embedded and Filter. I suggest describe specifically each method, considering the methods’ name used in the manuscript in a specific section. It is not clear what are the specificities of each method.

16) In Section 4.3, why were the models LGBM, KNN, SVM, and LR, chosen? It is important to include a brief discussion about them and the reason to choose them.

17) In Section 4.3, why were the KPIs, f recall rate, F1-Score, and precision, chosen? It is important to include a brief discussion about them the reason to choose them.

18) In Table 4, I suggest underlining the best results for each classification model.

19) In “As depicted in Table 4, the average scores for Recall, F1-Score, and Precision for RFRS are 87.37%, 87.41%, and 84.71%, respectively; for Spearman's rho, the corresponding scores are 82.06%, 87.1%, and 88.06%, respectively; and for the Filter method, the scores are 85.52%, 85.58%, and 86.23%, respectively. Comparatively, the Recall score of RFRS is 5.31% higher than that of Spearman's rho and 1.85% higher than the Filter method; its F1-Score is 0.31% higher than Spearman's rho and 1.83% higher than the Filter method; whereas its Precision score is 3.35% lower than Spearman's rho and 1.52% lower than the Filter method.”, the average values are not highlighted in the Table.

In the Conclusion, “current mainstream feature selection methods.”, please name the methods. In Conclusion, “, although the specific application scenarios still require researchers to make decisions based on actual needs.”, please be more specific.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Research on feature selection for AC contactor vibration signals based on regularized random forest with recursive selection

PONE-D-24-16516R1

Dear Dr. Qi,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Caio Bezerra Souto Maior, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: Thanks for the authors' effort to address all my comnents. I consider the paper as accepted. However, I still have two comments:

1. In Table 1, include the units between parentheses and not with "/".

2. The unit is not MHz/s.but MHz.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********