1537 search results for "Regression"

Example 8.6: Changing the reference category for categorical variables

September 21, 2010
By
Example 8.6: Changing the reference category for categorical variables

How can we change the reference category for a categorical variable? This question comes up often in a consulting practice.When including categorical covariates in regression models, there is a question of how to incorporate the categories. One simpl...

Read more »

Data Mining in A Nutshell

September 20, 2010
By
Data Mining in A Nutshell

# The following code may look rough, but simply paste into R or# a text editor (especially Notepad++) and it will look# much better.# PROGRAM NAME: MACHINE_LEARNING_R# DATE: 4/19/2010# AUTHOR : MATT BOGARD# PURPOSE: BASIC EXAMPLES OF MACHINE LEAR...

Read more »

A simple Metropolis-Hastings MCMC in R

September 17, 2010
By
A simple Metropolis-Hastings MCMC in R

While there are certainly good software packages out there to do the job for you, notably BUGS or JAGS, it is instructive to program a simple MCMC yourself. In this post, I give an educational example of the Bayesian equivalent of a linear regression, sampled by an MCMC with Metropolis-Hastings steps, based on an earlier…

Read more »

Principal Component Analysis (PCA) vs Ordinary Least Squares (OLS): A Visual Explanation

September 16, 2010
By
Principal Component Analysis (PCA) vs Ordinary Least Squares (OLS): A Visual Explanation

Over at stats.stackexchange.com recently, a really interesting question was raised about principal component analysis (PCA). The gist was “Thanks to my college class I can do the math, but what does it MEAN?” I felt like this a number of times in my life. Many of my classes were focused on the technical implementations they kinda

Read more »

A Not Quite Random Number Generator (NQRNG)

September 13, 2010
By
A Not Quite Random Number Generator (NQRNG)

I connected the instrumentation amplifier described in an earlier post to a piezoelectric transducer (buzzer) and made recordings at 5000 gain. The plot below shows 1000 such measurements over 1.0 seconds. There is a 4.0 second (at 1000Hz) sample of the data here piezo.csv. There is a clear sinusoidal signal in these data of about

Read more »

10w2170, Banff [2]

September 13, 2010
By
10w2170, Banff [2]

Over the two days of the Hierarchical Bayesian Methods in Ecology workshop, we managed to cover normal models, testing, regression, Gibbs sampling, generalised linear models, Metropolis-Hastings algorithms and of course a fair dose of hierarchical modelling. At the end of the Saturday marathon session, we spent one and half discussing some models studied by the

Read more »

Missing Data in R

September 12, 2010
By
Missing Data in R

Probably all of us have met the issue of handling missing data, from the basic portfolio correlation matrix estimation, to advanced multiple factor analysis, how to impute missing data remains a hot topic. Missing data are unavoidable, and more encompassing than the ubiquitous association of the term, irgoring missing data will generally lead to biased estimates. The...

Read more »

Confidence Bands for Universal Scalability Models

September 7, 2010
By
Confidence Bands for Universal Scalability Models

In the recent GDAT class, confidence intervals (CI) for performance data were discussed. Their generalization to confidence bands (CB) for scalability projections using the USL model also came up informally. I showed a prototype plot but it was an ugly hack. Later requests from GDAT attendees to apply CBs to their own data meant I had...

Read more »

Confidence Bands for Universal Scalability Models

September 7, 2010
By
Confidence Bands for Universal Scalability Models

In the recent GDAT class, confidence intervals (CI) for performance data were discussed. Their generalization to confidence bands (CB) for scalability projections using the USL model also came up informally. I showed a prototype plot but it was an ugly hack. Later requests from GDAT attendees to apply CBs to their own data meant I had...

Read more »

How the expiration of the assault weapon ban affected Mexico

September 2, 2010
By
How the expiration of the assault weapon ban affected Mexico

There has been a lot of attention paid to the role of US guns exacerbating the violence in Mexico. The assault-weapon ban expired on September 14, 2004, but with the recent spiraling of violence in Mexico the ban has attracted renewed attention. Just recently the Mexican President stood before the American Congress and blamed the assault weapon...

Read more »