Tag: Efficiency

Rick Wicklin 0
Evaluate polynomials efficiently by using Horner's scheme

Polynomials are used often in data analysis. Low-order polynomials are used in regression to model the relationship between variables. Polynomials are used in numerical analysis for numerical integration and Taylor series approximations. It is therefore important to be able to evaluate polynomials in an efficient manner. My favorite evaluation technique

Rick Wicklin 0
Multithreaded = more productive

When I write SAS/IML programs, I usually do my development in the SAS/IML Studio environment. Why? There are many reasons, but the one that I will discuss today is the fact that the application is multithreaded and supports multiple programming workspaces. The advantages of multiple programming workspaces I am always

Rick Wicklin 0
Complex assignment statements: CHOOSE wisely

This article describes the SAS/IML CHOOSE function: how it works, how it doesn't work, and how to use it to make your SAS/IML programs more compact. In particular, the CHOOSE function has a potential "gotcha!" that you need to understand if you want your program to perform as expected. What

Rick Wicklin 0
Pre-allocate arrays to improve efficiency

Recently Charlie Huang showed how to use the SAS/IML language to compute an exponentially weighted moving average of some financial data. In the commentary to his analysis, he said: I found that if a matrix or a vector is declared with specified size before the computation step, the program’s efficiency

Rick Wicklin 0
Finding data that satisfy a criterion

A fundamental operation in data analysis is finding data that satisfy some criterion. How many people are older than 85? What are the phone numbers of the voters who are registered Democrats? These questions are examples of locating data with certain properties or characteristics. The SAS DATA step has a

Analytics
Chuck Ellstrom 0
The Two E's

Unless you’ve been living under a rock, you’ve heard about the budget problems running rampant across all levels of government. Federal, State and Local Governments are all facing historic budget shortfalls due to the economic crisis and decreased tax receipts. This has led to a much closer examination of services

Rick Wicklin 0
How to sample from independent normal distributions

In my article on computing confidence intervals for rankings, I had to generate p random vectors that each contained N random numbers. Each vector was generated from normal distribution with different parameters. This post compares two different ways to generate p vectors that are sampled from independent normal distributions. Sampling

Advanced Analytics
Rick Wicklin 0
Sampling with replacement

Sampling with replacement is a useful technique for simulations and for resampling from data. Over at the SAS/IML Discussion Forum, there was a recent question about how to use SAS/IML software to sample with replacement from a set of events. I have previously blogged about efficient sampling, but this topic

Advanced Analytics
Rick Wicklin 0
Efficient Sampling

Recently, SAS Global Forum announced the call for papers for the 2011 conference to be held at Caesars Palace in Las Vegas. Since the conference is in Las Vegas, I’ve been thinking a lot about games of chance: blackjack, craps, roulette, and the like. You can analyze these games by