Binomial confidence intervals: exact vs. approximate
This graph and R code compares the exact vs. normal approximations for 95% binomial confidence intervals for n trials with either one success or 50% success.
Bar plot with error bars in R
Here’s a simple way to make a bar plot with error bars three ways: standard deviation, standard error of the mean, and a 95% confidence interval. The key step is to precalculate the statistics for ggplot2.
Calculate RMSE and MAE in R and SAS
Here is code to calculate RMSE and MAE in R and SAS. RMSE (root mean squared error), also called RMSD (root mean squared deviation), and MAE (mean absolute error) are both used to evaluate models. MAE gives equal weight to all errors, while RMSE gives extra weight to large errors.
Geolocate IP addresses in R
This R function uses the free freegeoip.net geocoding service to resolve an IP address (or a vector of them) into country, region, city, zip, latitude, longitude, area and metro codes.
Popup notification from R on Windows
After R is done running a long process, you may need to notify the operator to check the R console and provide the next commands. Without installing any more software or creating any batch files or VBS scripts, here is a simple way to create the popup notice in Windows
lag function for data frames
When applying the stats::lag() function to a data frame, you probably expect it will pad the missing time periods with NA, but lag() doesn’t. For example: Nothing happened. Here is an alternative lag function made for this situation. It pads the beginning of the output vecot with as many NA as there are lags, and…
nnet2sas() supports centering and scaling
nnet2sas() version 1 introduced a way to export a nnet() model trained in R to Base SAS through metaprogramming, and now nnet2sas() version 2 introduces support for variable centering and scaling as implemented in caret::train(). See the link for version 1 for more background on nnet2sas(). Update: This function and similar functions are now in…
Comparing continuous distributions with R
In R we’ll generate similar continuous distributions for two groups and give a brief overview of statistical tests and visualizations to compare the groups. Though the fake data are normally distributed, we use methods for various kinds of continuous distributions. I put this together while working with data from an odd distribution involving money where…
Plotting individual growth charts
This R code draws individual growth plots as shown in “Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence” by Judith D. Singer and John B. Willett, an excellent book on multilevel modeling and survival analysis. This code recreates figure 2.5 on page 32 with the caption, “OLS summaries of how individuals change over time.…
Scales and transformations in ggplot2 0.9.0
Some R code designed for ggplot2 0.8.9 is not compatible with ggplot2 0.9.0, and today the ggplot2 web site has outdated documentation which gives this broken example: Dennis Murphy points to the ggplot2 0.9.0 transition guide from where I derived a solution: The transition guide has more details about transformations such as log, log10, sqrt,…
Heuristic Andrew 