Handling Categorical Data in Machine Learning: Easy Explanation for Data Science Interviews

Handling categorical data in machine learning projects is a very common topic in data science interviews. In this video, I’ll cover the difference between treating a variable as a dummy variable vs. a non-dummy variable, how you can deal with categorical features when the number of levels is very large, and the pros and cons of various strategies.
Feature hashing
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Contents of this video:
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00:00 Introduction
00:48 Categorical Data
02:22 Ordinal Features & Class Labels
03:38 One-Hot Encoding
05:32 Dummy Encoding
06:30 Problems of One-Hot & Dummy Encoding
07:26 Feature Hashing

[@linghaoyi]

Thank you. Merry Christmas and Happy New Year!

[@emma_ding]

Many of you have asked me to share my presentation notes, and now… I have them for you! Download all the PDFs of my Notion pages at www.emmading.com/get-all-my-free-resources. Enjoy!

[@junlizhou7167]

Thanks for the informative video Emma! Love the Notion notes you created

[@emma_ding]

So glad you enjoyed it! Thank you for watching. 😊

[@qingxiawang161]

Hi, Emma, thank you very much for the informative video, I really learned a lot from it! Keep up the good work❤

[@hsuya3925]

Hi Emma, very informative video. Thanks for working on all these types of videos and sharing with us. Wanted to know is your notion page public? or can you share if possible.

[@Dr_Hermit]

I have been waitiing for these as well. :)

[@emma_ding]

Of course! I'm working on getting all notes organized and sharable in one location, will let you know as soon as they are ready! :)

[@emma_ding]

@sukumargv @hsuya3925 Here you go! You can now download all the PDFs of my Notion pages at www.emmading.com/get-all-my-free-resources. Enjoy!

[@nitishjambhurkar7990]

Hi Emma, thank you soo much for this insight. Addition to this i also want to know how to handle large datasets like very large datasets because i was asked in an interview but i was unable to answer it correctly. So wanted to know from you how to handle very huge datasets and how to load ? what steps you would take to load these datasets. If you can make one video on this topic that would be great.

[@jet3111]

Hi Emma, thank you for the very informative video. It would be great to discuss embedding methods for handling categorical data.

[@emma_ding]

Great suggestion! I've added it to my list of content ideas. 😊 Thanks for watching!

[@saudiorchestra6443]

How do we deal with a category that appears for the first time in the test data? For examples, I the training data I have a column for the jobs. The training data contains these jobs: Doctor, Nurse, Lab technician, Administrator I used one hot encoding for the job column. What if the test data has an additional job Surgeon? How do we handle this situation?

[@rakeshkumarsharma2250]

How I convert pincode /postal code

[@sruthimallarapu7662]

Hi Emma, Can decision trees handle string categorical values (For example "gender" column takes "M" or "F"). Is it not necessary to convert the strings to numericals?

[@georgezevallos]

All ML algorithms require to convert the strings into numerical values. Even NLP does it. Hope it helps.