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Analytics | Data Visualization | Programming Tips

Rick WicklinSeptember 3, 2019 8

An important application of the dot product (inner product) of two vectors is to determine the angle between the vectors. If u and v are two vectors, then cos(θ) = (u ⋅ v) / (|u| |v|) You could apply the inverse cosine function if you wanted to find θ in

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Data Visualization | Programming Tips

Rick WicklinAugust 28, 2019 2

Annotate features of a schematic box plot in SGPLOT

A SAS programmer asked an intriguing question on the SAS Support Communities: Can you use SAS to create a graph that shows how the elements in a box-and-whiskers plot relate to the data? The SAS documentation has several examples that explain how to read a box plot. One of the

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinJuly 15, 2019 4

Create a discrete heat map with PROC SGPLOT

Heat maps have many uses. You can use a heat map to visualize correlation matrices, to visualize longitudinal data ("lasagna plots"), and to visualize counts in any two-dimensional table. As of SAS 9.4m3, you can create heat maps in SAS by using the HEATMAP and HEATMAPPARM statements in PROC SGPLOT.

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Data Visualization | Programming Tips

Rick WicklinJuly 10, 2019 0

Find the center of each cell in a mosaic plot

I recently showed how to create an annotation data set that will overlay cell counts or percentages on a mosaic plot. A mosaic plot is a visual representation of a cross-tabulation of observed frequencies for two categorical variables. The mosaic plot with cell counts is shown to the right. The

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Data Visualization | Programming Tips

Rick WicklinJuly 8, 2019 3

How to add an annotation to a mosaic plot in SAS

The mosaic plot is a graphical visualization of a frequency table. In previous articles, I showed how to create a mosaic plot in SAS by using PROC FREQ and how to define a template in the Graph Template Language (GTL) by using the MOSAICPARM statement. This article shows how to

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Data Visualization

Rick WicklinJuly 1, 2019 10

Visualize race times in SAS

Math and statistics are everywhere, and I always rejoice when I spot a rather sophisticated statistical idea "in the wild." For example, I am always pleased when I see a graph that shows the distribution of race times in a typical race (such as a 5K), as shown to the

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Analytics | Data Visualization | Learn SAS

Rick WicklinJune 24, 2019 0

Add loess smoothers to residual plots

When fitting a least squares regression model to data, it is often useful to create diagnostic plots of the residuals versus the explanatory variables. If the model fits the data well, the plots of the residuals should not display any patterns. Systematic patterns can indicate that you need to include

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Analytics | Data Visualization | Learn SAS

Rick WicklinJune 19, 2019 1

Influential observations in a linear regression model: The DFFITS and Cook's D statistics

A previous article describes the DFBETAS statistics for detecting influential observations, where "influential" means that if you delete the observation and refit the model, the estimates for the regression coefficients change substantially. Of course, there are other statistics that you could use to measure influence. Two popular ones are the

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Analytics | Data Visualization | Learn SAS

Rick WicklinJune 17, 2019 11

Influential observations in a linear regression model: The DFBETAS statistics

My article about deletion diagnostics investigated how influential an observation is to a least squares regression model. In other words, if you delete the i_th observation and refit the model, what happens to the statistics for the model? SAS regression procedures provide many tables and graphs that enable you to

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinJune 5, 2019 2

Plot a family of curves in SAS

A family of curves is generated by an equation that has one or more parameters. To visualize the family, you might want to display a graph that overlays four of five curves that have different parameter values, as shown to the right. The graph shows members of a family of

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