How far away is the nearest hospital? How far is the nearest restaurant? The nearest gas station? These are commonly asked questions whose answers depend on the location of the person asking the question. Recently I showed an algorithm that enables you to find the distance between a set of
What is weighted regression? How does it differ from ordinary (unweighted) regression? This article describes how to compute and score weighted regression models. Visualize a weighted regression Technically, an "unweighted" regression should be called an "equally weighted " regression since each ordinary least squares (OLS) regression weights each observation equally.
The recent releases of SAS 9.4 have featured major enhancements to the ODS statistical graphics procedures such as PROC SGPLOT. In fact, PROC SGPLOT (and the underlying Graph Template Language (GTL)) are so versatile and powerful that you might forget to consider whether you can create a graph automatically by
My son is taking an AP Statistics course in high school this year. AP Statistics is one of the fastest-growing AP courses, so I welcome the chance to see topics and techniques in the course. Last week I was pleased to see that they teach data exploration techniques, such as
In the area of graphical visualization of data, Edward Tufte is a thought leader and has put forth many innovative ideas that enhance the understanding of the information in the graph with minimal distractions and potential for misinterpretation. One of his ideas has been the use of "Spark" plots. As per my
Although statisticians often assume normally distributed errors, there are important processes for which the error distribution has a heavy tail. A well-known heavy-tailed distribution is the t distribution, but the t distribution is unsuitable for some applications because it does not have finite moments (means, variance,...) for small parameter values.
If you use SAS® software to create a report that contains multiple graphs, you know that each graph appears on a separate page by default. But now you want to really impress your audience by putting multiple graphs on a page. Keep reading because this blog post describes how to
In this post, I will show you how to control the order of the entries in a legend and explicitly control the correspondence between groups and style elements in PROC SGPLOT. In many cases, the colors that are used to differentiate groups do not matter--the graph simply needs to display
One of the strengths of the SGPLOT procedure in SAS is the ease with which you can overlay multiple plots on the same graph. For example, you can easily combine the SCATTER and SERIES statements to add a curve to a scatter plot. However, if you try to overlay incompatible
The article uses the SAS DATA step and Base SAS procedures to estimate the coverage probability of the confidence interval for the mean of normally distributed data. This discussion is based on Section 5.2 (p. 74–77) of Simulating Data with SAS. What is a confidence interval? Recall that a confidence
Last week I wrote about how to compute sample quantiles and weighted quantiles in SAS. As part of that article, I needed to draw some step functions. Recall that a step function is a piecewise constant function that jumps by a certain amount at a finite number of points. Graph
Many univariate descriptive statistics are intuitive. However, weighted statistic are less intuitive. A weight variable changes the computation of a statistic by giving more weight to some observations than to others. This article shows how to compute and visualize weighted percentiles, also known as a weighted quantiles, as computed by
Often I have written articles that are motivated by some question by a user on how to create a particular graph, or how to work around some shortcoming in the feature set to create the graph you need. This time, I got a question about Clinical Graphs that were mostly working
Last week I was visiting San Diego for the SANDS conference. I always enjoy this conference as I get to interact closely with the users to hear of their pains and innovative solutions to creating Clinical Graphs. In the conference Ed Barber asked about displaying A1c data along with some
A common question is "how do I compute a bootstrap confidence interval in SAS?" As a reminder, the bootstrap method consists of the following steps: Compute the statistic of interest for the original data Resample B times from the data to form B bootstrap samples. How you resample depends on
A few weeks back I posted an article on ways to create a WindRose Graph using SGPLOT procedure. The process is relatively simple. Create (R, Theta) data with both numeric axes where the Theta is a value in the data range is 0-360, and R is the corresponding response value. Then
In a scatter plot, the regions where observations are packed tightly are areas of high density. A contour plot or heat map of a bivariate kernel density estimate (KDE) is one way to visualize regions of high density. A SAS customer asked whether it is possible to use SAS to
A kernel density estimate (KDE) is a nonparametric estimate for the density of a data sample. A KDE can help an analyst determine how to model the data: Does the KDE look like a normal curve? Like a mixture of normals? Is there evidence of outliers in the data? In
There was a recent comment on the original 'Unbox Your Box Plots', where a user wants to see the original data for the box, but only label the outliers. As noted in the comment, labeling all the scatter markers and turning on the outlier display is not ideal. But there
This weekend I was reviewing my portfolio of stocks as usual. Yes, I do have a small stock portfolio with a few stocks, and normally I use free stock charting software to review the stock plots. These sites allow you to view the daily stock prices along with many technical
One of my favorite new features in PROC SGPLOT in SAS 9.4m2 is addition of the COLORRESPONSE= and COLORMODEL= options to the SCATTER statement. By using these options, it is easy to color markers in a scatter plot so that the colors indicate the values of a continuous third variable.
As often is the case, this article is prompted by a recent post on the SAS/GRAPH and ODS Graphics page communities page. A user wanted to create a Graph Table showing a bar chart with tabular data for each of the category values along the x-axis. The user was creatively using
Stellen Sie sich vor, Sie sind frühmorgens mit dem Auto „ab in den Urlaub“ gefahren. Durch vorausschauende Routenplanung sind Sie den größten Staurisiken glücklich ausgewichen und nähern sich bei geschätzten 38°C der letzten Landesgrenze vor Ihrem Urlaubsziel. Die ganze Familie sitzt mit ausgelassener Stimmung im vollgepackten Auto. Die Kinder auf
Today is #EmbraceYourGeekness day, and you are either reveling in this new crazy town inhabited by Pokémon GO, or you are hiding in your house trying to avoid all of the Pokémon GO zombies wandering around. But since I'm living in SAS these days -- not just the place (at
Last week I posted an article on displaying polar graph using SAS. When the measured data (R, Theta) are in the polar coordinates as radius and angle, then this data can be easily transformed into the XY space using the simple transform shown below. x=r*cos(theta * PI / 180); y=r*sin(theta * PI
There are many situations where it is beneficial to display the data using a polar graph. Often your data may contain directional information. Or, the data may be cyclic in nature, with information over time by weeks, or years. The simple solution is to display the directional or time data
I recently read an article in which the winner of a Kaggle Competition was not shy about sharing his technique for winning not one, but several of the analytical competitions. “I always use Gradient Boosting,” he said. And then added, “but the key is Feature Engineering.” A couple days later,
Recently, I needed to view the list of products with the highest number of defects. I have a data set of defects reported against various products. The data set has over 30 products, and each observation contains the product name, name of the primary support person, and other relevant details of
At the most recent SAS Global Forum in Las Vegas, I gave a demo on using SAS/OR to compute an optimal strategy for the casino game blackjack. For anyone who wasn't able to attend, I'd like to show some of the code and results here.
A Turnip Graph displays the distribution of an analysis variable. The graph displays markers with the same (or close) y coordinate by displaying the markers spread out over the x-axis range in a symmetric pattern. Recently, a question was posted on the SAS Communities page regarding such a graph. Here is an example of
