Data Mining: Hash tree based support counting

Data Mining: Hash Tree based support counting

Hash tree is a very quick way to search an item. When there are many itemsets, hash tree could be used to find out if a given itemset has got required support count. But, how do we construct hash tree? The links I came across were very abstarct to define the hash tree implementation.

Suppose we want to insert (i.e. hash)
the following 3-itemsets into the tree

We have taken hashing function h(x) = N mod 3. This has three possible values for h(x) = {0, 1, 2}. Each value is a branch of a Hash tree node. So, each node will have three branches.

Now, lets insert Itemsets = {8, 7, 5} {9, 3, 6}

Start with I1 = {8, 7, 5}


Remember, that we are considering 8 because it is lavel 1 of the tree. Next level, we will consider 7 and the next with 5.

The first item = 8
h(8) = 8 mod 3 = 2


I2 = {9, 3, 6}
The first item = 9
h(9) = 9 mod 3 = 0


Level 1
Now, the secons item of set I1 = 7
h(7) = 7 mod 3 = 1


Now, the secons item of set I2 = 3
h(7) = 3 mod 3 = 0



A gold mine: Data mining

A science to sift through huge data-set and make out useful interpretations, means Data Mining to me. It is a very interesting way to find out “behavior” from data. During my graduation, I could never appreciate usefulness of data analysis for non-technical purposes aka business decision making.

But, probably maturity is dawning upon me 😉 It is such an exciting field that employs statistics, computer science and businesses. Tools including decision trees, rule based classifier are based on fundamentals of Information theory (Entropy, Information gain, Euclid distances) and could be implemented with ease on huge data-sets with emerging technologies like Hadoop.

My introduction to mining like methodology my professional work was based on Application performance profilers. This tool could collect and save samples on active application and later these samples were analyzed to make various interpretations on application performance.

Data mining is an interesting, promising field and I am keen to delve more into it.