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The figure below plots the training data and the actual decision boundary.

scatter
Scatter Plot of Training Data

We split the training data set into 3 separate sets, training set with 600 examples, cross-validation set with 200 examples and test data set with 200 examples.

Classification

This training data was then fed into a logistic regression classifier to study the performance of the classifier. It is important to note that the objective of logistic regression classifier is maximizing the accuracy of labeling the data into two classes. Unlike linear regression, the decision boundary of the logistic regression classifier does not try to match the underlying true boundary which divides the data into two classes.

In addition to the two features that identify a training example, polynomial features up to a desired degree are generated. We start off the optimization with an initial parameter value of all 0. The optimization of the cost function is done using the Matlab's built-in fminunc function. A function costFunctionReg.m that outputs the regularized cost and regularized gradient, with the training data, parameter values and the regularization parameter as inputs, is given as input along with initial parameter values to this fminunc function.

Now we vary the maximum degree of the polynomial features to study the decision boundary of the classifier. Its important to note that the values of the parameters are obtained from the training data set, for a given value of maximum degree. The optimal values of maximum degree are determined by the performance on the cross-validation set. Finally, the decision boundary obtained by solving for the parameters with optimal values of maximum degree is used to evaluate the performance on a test data set, in order to see how well the classifier generalizes.

The decision boundary for a degree 1 polynomial is shown in [link] below. The accuracy on the cross-validation set was 84 . 50 .

regress
Logistic Regression with 1st degree features

From [link] it is clear that 1 st degree features are not sufficient to capture both classes. So the maximum degree was increased to 2. [link] plots the decision boundary for degree 2. The accuracy of the classifier on cross-validation set in this case was 98 . 50 .

regress2
Logistic Regression with 2nd degree features

We now try the maximum degree of 3. [link] plots the decision boundary with maximum degree 3. The accuracy on cross-validation set is 98.00.

regress3
Logistic Regression with 3rd degree features

Due to its lower accuracy, the logistic regression classifier with maximum degree 2 is chosen from amongst the 3 classifiers. This classifier was then evaluated on test data set to study how well it generalizes. The accuracy of this classifier on test set was 98.00. Hence this logistic regression classifier generalizes very well.

To see the MATLAB code that generated these plots, download the following .zip file: MATLAB files for simulated data. !

Conclusion

As was stated, this collection is intended to be an introduction to regression analysis, but is sufficient in order to understand the application of logistic regression to an application. There are plenty of resources to learn more about more nuanced views of the key components of the theory, and more resources to see logistic regression in action!

For an application of Logistic Regression to a synthetic dataset and to a real-world problem in statistical physics, see Optimizing Logistic Regression for Particle Physics !

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Introductory survey and applications of machine learning methods. OpenStax CNX. Dec 22, 2011 Download for free at http://legacy.cnx.org/content/col11400/1.1
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