LFD Book Forum  

Go Back   LFD Book Forum > Course Discussions > Online LFD course > Homework 2

Reply
 
Thread Tools Display Modes
  #1  
Old 04-17-2012, 07:45 PM
ShengrongYIN ShengrongYIN is offline
Junior Member
 
Join Date: Apr 2012
Posts: 2
Default How to do the homework?

It would be very appreciated for your help! I was totally exhausted with the homework. I want to know whether it is necessary to do the homework with some computer tools(like Octove or Matlab), if so ,how can I solve these problems using these tools. I may not understand the problem well. Is there any online tutorial to solve the problems step by step?
Reply With Quote
  #2  
Old 04-17-2012, 09:05 PM
dudefromdayton dudefromdayton is offline
Invited Guest
 
Join Date: Apr 2012
Posts: 140
Default Re: How to do the homework?

You ask some very good questions. If you're exhausted, I might suggest making an educated guess at some of the answers. Alternatively, you might be able to eliminate some of the alternatives. For the first two homework sets, I found a strong correlation between the estimates I could make without a computer, and the experimental results obtained after a lot more work.
Reply With Quote
  #3  
Old 04-17-2012, 09:17 PM
magdon's Avatar
magdon magdon is offline
RPI
 
Join Date: Aug 2009
Location: Troy, NY, USA.
Posts: 595
Default Re: How to do the homework?

Indeed, if you are doing the homework manually, I am not surprised at all that you are exhausted. I would be dead. You are expected to build computer programs to solve the problems by implementing the algorithms. Convenient languages to work with are matlab, octave, R, python.

Quote:
Originally Posted by ShengrongYIN View Post
It would be very appreciated for your help! I was totally exhausted with the homework. I want to know whether it is necessary to do the homework with some computer tools(like Octove or Matlab), if so ,how can I solve these problems using these tools. I may not understand the problem well. Is there any online tutorial to solve the problems step by step?
__________________
Have faith in probability
Reply With Quote
  #4  
Old 04-18-2012, 07:39 PM
Hillbilly Hillbilly is offline
Invited Guest
 
Join Date: Mar 2012
Location: West Virginia
Posts: 45
Default Re: How to do the homework?

@dudefromdayton, your remarks stir curiosity. Could you be more specific please, as with an example, of how to make an "educated guess" on these homeworks (that's correct!)? Does doing so presume prior education on the subject of the questions (beyond the basic prerequisites stated)? How can one make an educated guess when not yet educated on the subject? I'm not trying to be snarky, just curious about what you mean.

I, too, found the homeworks time-consuming and somewhat tiring, and would love to know any shortcuts! I did OK in the end, but it took a lot of work, suggesting that my understanding is shallow.

Even more curious, how did you make reasonable estimates for any of the problems requiring simulations? Did you use relationships, equations, etc. known to practitioners, but not mentioned in class yet? For example, results reported from the Homework 1 PLA simulation suggest that iterations to convergence is close to N, the training set size (for randomly choosing a misclassification to update). If that hypothesis is correct, and was known beforehand, then of course, answering correctly was trivial without doing the programming.

Would appreciate any helpful hints. Thanks!

Quote:
Originally Posted by dudefromdayton View Post
If you're exhausted, I might suggest making an educated guess at some of the answers. ..... For the first two homework sets, I found a strong correlation between the estimates I could make without a computer, and the experimental results obtained after a lot more work.
Reply With Quote
  #5  
Old 04-19-2012, 10:30 AM
dudefromdayton dudefromdayton is offline
Invited Guest
 
Join Date: Apr 2012
Posts: 140
Default Re: How to do the homework?

I would like to, and Yaser knows what I have in mind. Let me make sure it's appropriate here before I post!
Reply With Quote
  #6  
Old 04-26-2012, 09:39 PM
dudefromdayton dudefromdayton is offline
Invited Guest
 
Join Date: Apr 2012
Posts: 140
Default Re: How to do the homework?

@Hillbilly, I don't want to overstep on this topic. But have a look at problem 9 (in the second homework set). Start from the target function:

f(x1, x2) = sign(x1^2 + x2^2 - 0.6)

Notice that it's symmetric in x1 and x2? What's that suggest to you about choices b, c, and d? Why would the two strongest coefficients in the polynomial differ by tenfold between these variables? And choice e, how does the x1x2 term become so significant compared to the others? In fact, what would the geometric significance of the x1x2 term be in terms of classification?

Let's also look at problem 10, which uses the same target function and illustrates a similar point. The target function wasn't originally linearly separable, but your transformation definitely made it so. This means you're running linear regression on a linearly separable set of data, and you have a fairly large set of it. How much error will this result in? A lot? Medium? Very little? But the target function has 10% noise, which depending on what you decided on my last question, E[out] will be 10% + a lot, 10% + somewhat, or 10% + negligible.

In general, it is not easy to write multiple-choice problem sets on advanced topics. Just ask the folks who write questions for the SAT! Not long ago, it was possible to answer reading comprehension questions without reading the passage -- just pick the answer which wouldn't cast any group of people in a bad light. It was also possible to identify (and skip) entire sections of the exam which would not be graded.
Reply With Quote
  #7  
Old 05-02-2012, 07:14 AM
Hillbilly Hillbilly is offline
Invited Guest
 
Join Date: Mar 2012
Location: West Virginia
Posts: 45
Default Re: How to do the homework?

@dudefromdayton, thank you for those examples of "off-the-cuff" reasoning (I assume that's an appropriate term). I ended up doing something similar on Homework 4, for lack of time. For example, I intended to try both analytical and brute-force simulation approaches to solving #7 (which learning model has least out-of-sample error), but some other problems used up my time quota. So I employed rough-and-ready reasoning, and got the right answer (I claim no victory, however, given the 20% chance of a random guess being right!).

I think it's a good idea to employ multiple methods, if enough time -- mathematical analysis, numerical examples, simulation, graphical methods, even intuition. If they all produce the same answer, the problem is mastered; if not, then something needs fixing!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 07:25 PM.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
The contents of this forum are to be used ONLY by readers of the Learning From Data book by Yaser S. Abu-Mostafa, Malik Magdon-Ismail, and Hsuan-Tien Lin, and participants in the Learning From Data MOOC by Yaser S. Abu-Mostafa. No part of these contents is to be communicated or made accessible to ANY other person or entity.