Posts Tagged ‘ data analysis ’

When is a histogram not a histogram? When it’s a table!

December 5, 2018
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When is a histogram not a histogram? When it’s a table!

Recently a SAS programmer wanted to obtain a table of counts that was based on a histogram. I showed him how you can use the OUTHIST= option on the HISTOGRAM statement in PROC UNIVARIATE to obtain that information. For example, the following call to PROC UNIVARIATE creates a histogram for

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Singular parameterizations, generalized inverses, and regression estimates

November 28, 2018
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Singular parameterizations, generalized inverses, and regression estimates

I remember the first time I used PROC GLM in SAS to include a classification effect in a regression model. I thought I had done something wrong because the parameter estimates table was followed by a scary-looking note: Note: The X'X matrix has been found to be singular, and a

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A funnel plot for immunization rates

November 26, 2018
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A funnel plot for immunization rates

Last week my colleague, Robert Allison, visualized data regarding immunization rates for kindergarten classes in North Carolina. One of his graphs was a scatter plot that displayed the proportion of unimmunized students versus the size of the class for 1,885 kindergarten classes in NC. This scatter plot is the basis

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Generalized inverses for matrices

November 21, 2018
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A data analyst asked how to compute parameter estimates in a linear regression model when the underlying data matrix is rank deficient. This situation can occur if one of the variables in the regression is a linear combination of other variables. It also occurs when you use the GLM parameterization

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Create and compare ROC curves for any predictive model

November 14, 2018
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Create and compare ROC curves for any predictive model

An ROC curve graphically summarizes the tradeoff between true positives and true negatives for a rule or model that predicts a binary response variable. An ROC curve is a parametric curve that is constructed by varying the cutpoint value at which estimated probabilities are considered to predict the binary event.

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Fit the Pareto distribution in SAS

November 5, 2018
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Fit the Pareto distribution in SAS

Will the real Pareto distribution please stand up? SAS supports three different distributions that are named "Pareto." The Wikipedia page for the Pareto distribution lists five different "Pareto" distributions, including the three that SAS supports. This article shows how to fit the two-parameter Pareto distribution in SAS and discusses the

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Parameter estimates for different parameterizations

October 17, 2018
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Parameter estimates for different parameterizations

In a recent article about nonlinear least squares, I wrote, "you can often fit one model and use the ESTIMATE statement to estimate the parameters in a different parameterization." This article expands on that statement. It shows how to fit a model for one set of parameters and use the

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Get the unique values of a variable in data order

October 15, 2018
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Get the unique values of a variable in data order

There are several ways to use SAS to get the unique values for a data variable. In Base SAS, you can use the TABLES statement in PROC FREQ to generate a table of unique values (and the counts). You can also use the DISTINCT function in PROC SQL to get

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