## Data Visualization

Get the right information, with visual impact, to the people who need it

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Generate random uniform points in an ellipse

I have previously written about how to efficiently generate points uniformly at random inside a sphere (often called a ball by mathematicians). The method uses a mathematical fact from multivariate statistics: If X is drawn from the uncorrelated multivariate normal distribution in dimensiond, then S = r*X / ||X|| has

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IA en la nube: una nueva era empresarial

Con un tamaño estimado de más de 619 mil millones de dólares para 2023, la computación en la nube es un mercado que cada año crece en tamaño y complejidad, pero que al mismo tiempo aumenta sus posibilidades gracias a las soluciones analíticas y de Inteligencia Artificial que ayudan a

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How to use a log-scale on a histogram

Real-world data often exhibits extreme skewness. It is not unusual to have data span many orders of magnitude. Classic examples are the distributions of incomes (impoverished and billionaires) and population sizes (small countries and populous nations). The readership of books and blog posts show a similar distribution, which is sometimes

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How does PROC SGPLOT position labels for polygons?

Labeling objects in graphs can be difficult. SAS has a long history of providing support for labeling markers in scatter plots and for labeling regions on a map. This article discusses how the SGPLOT procedure decides where to put a label for a polygon. It discusses the advantages and disadvantages

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Compute the silhouette statistic in SAS

A previous article defines the silhouette statistic (Rousseeuw, 1987) and shows how to use it to identify observations in a cluster analysis that are potentially misclassified. The article provides many graphs, including the silhouette plot, which is a bar chart or histogram that displays the distribution of the silhouette statistic

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The Empirical Mode Decomposition for handling non-stationary time series

Empirical Mode Decomposition (EMD) is a powerful time-frequency analysis technique that allows for the decomposition of a non-stationary and non-linear signal into a series of intrinsic mode functions (IMFs). The method was first introduced by Huang et al. in 1998 and has since been widely used in various fields, such as signal processing, image analysis, and biomedical engineering.

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What is the silhouette statistic in cluster analysis?

Assigning observations into clusters can be challenging. One challenge is deciding how many clusters are in the data. Another is identifying which observations are potentially misclassified because they are on the boundary between two different clusters. Ralph Abbey's 2019 paper ("How to Evaluate Different Clustering Results") is a good way

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Overlay a curve on a histogram in SAS

In a previous article, I showed how to overlay a density estimate on a histogram by using the Graph Template Language (GTL). However, a SAS programmer asked how to overlay a curve on a histogram when the curve is not a density estimate. In this case, the vertical axis for

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Compatible plot types in SAS

When the SAS statistical graphics (SG) procedures were designed in the early 2000s, a goal was to create a comprehensive Graph Template Language (GTL) and leverage the GTL by using SG procedures that perform common tasks easily without having to write any GTL. This project was hugely successful, and "ODS

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A random walk inside a heart

SAS programmers love to make special graphs for Valentine's Day. In fact, there is a long history of heart-shaped graphs and love-inspired programs written in SAS! Last year, I added to the collection by showing how a ball bounces on a heart-shaped billiards table. This year, I create a similar

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Colorblind-safe palettes in SAS

SAS supports the ColorBrewer system of color palettes from the ColorBrewer website (Brewer and Harrower, 2002). The ColorBrewer color ramps are available in SAS by using the PALETTE function in SAS IML software. The PALETTE function supports all ColorBrewer palettes, but some palettes are not interpretable by people with color

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Tips for making colorblind-safe statistical graphs

Did you know that about 8% of the world's men are colorblind? (More correctly, 8% of men are "color vision deficient," since they see colors, but not all colors.) Because of the "birthday paradox," in a room that contains eight men, the probability is 50% that at least one is

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El papel de la inteligencia empresarial y analítica en el futuro de las BFSI

Cuando se habla de Big Data en la industria BFSI (como es conocida a nivel internacional la industria de servicios financieros incluyendo banca y seguros), se hace referencia a oportunidades, crecimiento, transformación y futuro. Muy pocas industrias tienen, generan y agregan tantos datos como la de los servicios financieros. Para comenzar, las empresas de esta industria deben entender y analizar más que muchas otras el comportamiento de los clientes, no solo por el cumplimiento de normas, sino también por

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Art in SAS: Christmas wrapping paper

For Christmas 2021, I wrote an article about palettes of Christmas colors, chiefly shades of red, green, silver, and gold. One of my readers joked that she would like to use my custom palette to design her own Christmas wrapping paper! I remembered her jest when I saw some artwork

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Optimal linear profile plots in SAS

A profile plot is a way to display multivariate values for many subjects. The optimal linear profile plot was introduced by John Hartigan in his book Clustering Algorithms (1975). In Michael Friendly's book (SAS System for Statistical Graphics, 1991), Friendly shows how to construct an optimal linear profile by using

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Profile plots in SAS

A profile plot is a compact way to visualize many variables for a set of subjects. It enables you to investigate which subjects are similar to or different from other subjects. Visually, a profile plot can take many forms. This article shows several profile plots: a line plot of the

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The area of the convex hull of random points

I recently blogged about how to compute the area of the convex hull of a set of planar points. This article discusses the expected value of the area of the convex hull for n random uniform points in the unit square. The article introduces an exact formula (due to Buchta,

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Visualize dependencies of missing values

A SAS programmer asked how to create a graph that shows whether missing values in one variable are associated with certain values of another variable. For example, a patient who is supposed to monitor his blood glucose daily might have more missing measurements near holidays and in the summer months

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Export a Visual Analytics report using REST APIs

In my previous blog Programmatically export a Visual Analytics report to PDF - SAS Users, I use the SAS Visual Analytics SDK to export a report to PDF, which is quite simple if we have basic knowledge with JavaScript programming. It works for both the latest version of SAS Viya

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Complex Layouts using the SG Procedures

The Graph Template Language (GTL) is a powerful tool for creating a wide range of graphic displays. One feature GTL has is the ability to combine independent plots together into one paneled display. The SG procedures have some limited capabilities in this area; but in this post, I am going

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Analyzing demographics and patterns-of-life using SAS Visual Analytics

The IEEE Visual Analytics Science and Technology (VAST) Challenge provides a great opportunity to validate our software against real-world scenarios using complex data sets. Not only do we learn from these projects, but we also send feedback to our development teams to further improve product capabilities for customers.

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Data observability generates benefits well beyond migration management

My recent work has focused heavily on migration, especially onto the SAS Viya platform and cloud more generally. Rather unexpectedly during this process, we have found that data observability is becoming increasingly important to customers. They start simply by looking at tracing files, but soon find that it has a