## Saturday, 16 January 2016

### WHAT IS MACHINE LEARNING

WHAT IS MACHINE LEARNING?
Hello everyone! Happy new year to you all. Sorry for the delay in making this post, just started NYSC for real and believe me it's quite stressful but there have fun times too (I guess). Anyway, enough chit-chat let's get to the topic of the day - What is machine learning? This for me is a good place to start for anyone who has an interest in any topic (not just machine learning). What really is the thing I am interested in? That's the first question that I feel should be clearly answered. The objective of the post is to briefly define machine learning and give some of its popular applications.
According to Wikipedia, machine learning explores the study and construction of algorithms that can learn to make predictions from data rather than following static program instructions. Let me explain, machine learning uses data to make predictions. These predictions could be anything from the saying what the weather will be tomorrow, to classifying a handwritten digit, recognizing a picture or predicting what the price of an item will be given features of said item.
All of the tasks just mentioned would be difficult to achieve using rigid programming rules. For example, a classic problem in machine learning is classification of hand-written digits. Suppose we wanted to define what the digit '7' should look like, how would we do that? This would be difficult to do because people have different ways of writing the number '7'. Trying to write rules to define what the digit '7' is (or isn't) to a program would be difficult. In this case, the best option would be for the program to 'learn' the various parameters required to correctly classify a digit. To do this, we would collect samples of hand-written digits (data) which we would now feed to a machine learning algorithm. The output of this algorithm can now be used to classify digits.
Now that you know what machine learning is, let's look at some of its major uses (if you feel there others, please feel free to add them in the comments section). Machine learning is used mainly for prediction like I mentioned earlier. This can be further classified into:
i.                    Regression
ii.                  Classification
In regression, we use numbers to predict numbers. Let me use the popular example of trying to predict the price of a house. Assume we trying to predict the price of a house and that we also features (also called attributes) of this house e.g. square footage, number of bedrooms, number of bathrooms, the year it was built and so on. The task is given all these features (which are basically numbers) can predict how much this house will sell for? (another number).
Classification is more like regression – the only difference in this case is that we are trying to predict a class. Another popular example for classification is spam filtering where we use features of an email such the words in the email, sender’s name, sender’s IP address etc. to predict if the email is spam or not. This is called binary classification because we trying to predict which of two classes an email (or the item to be classified) belongs to. Sometimes, there may be more than two classes. In this case it’s called multi-class classification. A good example is classification of hand-written digits where we try to predict if a digit belongs of 1 out of a possible 10 classes.
Another application of machine learning I would to mention is in the area of products recommendation. This application is used by extensively by companies such as Amazon (to recommend what shoppers may like to buy) and Netflix (to recommend movies to users). Machine learning also finds application in areas such as image recognition and classification where neural networks are used to recognize and /or classify an image.

I hope this post has clearly explained what machine learning is and its application. Please feel free to drop a comment about anything that is unclear to you. Thanks for reading my blog. Hope to see you soon.  Cheers!!!