The Isomap Algorithm
This is part of a series on a family of dimension-reduction algorithms called non-linear dimension reduction. The goal here is to reduce the dimensions of a dataset (i.e. discard some columns in your data) In previous posts, I discussed the MDS algorithm and presented some key ideas. In this post, I will describe how those ideas are leveraged in the Isomap algorithm. A clojure implementation based
Efficiently Computing Kendall's Tau - adereth
Typically when people talk about correlation they are referring to the Pearson’s product-moment coefficient: $$\rho_{X,Y}={E[(X-\mu_X)(Y-\mu_Y)] \over \sigma_X\sigma_Y}$$ The Pearson coefficient is 1 if the datasets have a perfectly positive linear relationship and -1 if they have a perfectly negative linear relationship. But what if our data has a clear positive relationship, but it’s not linear?
Understanding Clojure's Persistent Vectors, pt. 2
In the previous post about Clojure’s persistent vectors (read it, if you haven’t already), we kind-of understood how insertion, updates and popping elements in a vector worked. We did not really understand how to get to the right element, and I will cover that along with how lookup works in this post. To understand how we pick the right branch, I think it’s good to give the proper name of the stru
Understanding Clojure's Persistent Vectors, pt. 1
★ Understanding Clojure's Persistent Vectors, pt. 1 posted 25 Sep 2013 You may or may not heard about Clojure’s persistent vectors. It is a data structure invented by Rich Hickey (influenced by Phil Bagwell’s paper on Ideal Hash Trees) for Clojure, which gives practically O(1) runtime for appends, updates, lookups and subvec. As they are persistent, every modification creates a new vector instead
Consistent Hashing with Clojure
Consistent Hashing with Clojure Let's say you want to distribute some objects to a number of nodes. The Naive approach to this problem would be to hash the object you want to store, then using the modulus operator pick a node and store it there, (mod (hash obj) n) This scheme would work until you add or remove nodes from the cache, now because you pick nodes from a pool of (+ n 1) or (- n 1) nodes
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Purely functional data structures in Clojure: Leftist Heaps
Purely functional data structures in Clojure: Red-Black Trees
