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Rick WicklinSeptember 8, 2020 1

Matrix balancing: Update matrix cells to match row and column sums

Matrix balancing is an interesting problem that has a long history. Matrix balancing refers to adjusting the cells of a frequency table to match known values of the row and column sums. One of the early algorithms for matrix balancing is known as the RAS algorithm, but it is also

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Programming Tips

Rick WicklinSeptember 2, 2020 0

The HighLow plot: When a stacked bar chart is not enough

The HighLow plot often enables you to create many custom plots without resorting to annotation. Although it is designed to create a candlestick chart for stocks, it is incredibly versatile. Recently, a SAS programmer wanted to create a patient-profile graph that looked like a stacked bar chart but had repeated

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Learn SAS | Programming Tips

Rick WicklinAugust 31, 2020 15

The best way to generate dummy variables in SAS

On discussion forums, many SAS programmers ask about the best way to generate dummy variables for categorical variables. Well-meaning responders offer all sorts of advice, including writing your own DATA step program, sometimes mixed with macro programming. This article shows that the simplest and easiest way to generate dummy variables

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Programming Tips

Rick WicklinAugust 26, 2020 0

Rewinding random number streams: An application

In the paper "Tips and Techniques for Using the Random-Number Generators in SAS" (Sarle and Wicklin, 2018), I discussed an example that uses the new STREAMREWIND subroutine in Base SAS 9.4M5. As its name implies, the STREAMREWIND subroutine rewinds a random number stream, essentially resetting the stream to the beginning.

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Learn SAS | Programming Tips

Rick WicklinAugust 24, 2020 6

How does PROC FCMP store functions?

I got a lot of feedback about my recent article about how to find roots of nonlinear functions by using the SOLVE function in PROC FCMP. A colleague asked how the FCMP procedure stores the functions. Specifically, why the OUTLIB= option on the PROC FCMP statement use a three-level syntax:

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Programming Tips

Rick WicklinAugust 19, 2020 5

Find the root of a function by using the SAS DATA step

Finding the root (or zero) of a nonlinear function is an important computational task. In the case of a one-variable function, you can use the SOLVE function in PROC FCMP to find roots of nonlinear functions in the DATA step. This article shows how to use the SOLVE function to

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Rick WicklinAugust 17, 2020 2

Estimate a power curve in parallel in SAS Viya

I recently showed how to use simulation to estimate the power of a statistical hypothesis test. The example (a two-sample t test for the difference of means) is a simple SAS/IML module that is very fast. Fast is good because often you want to perform a sequence of simulations over

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Learn SAS | Programming Tips

Rick WicklinAugust 12, 2020 2

Use simulation to estimate the power of a statistical test

A previous article about standardizing data in groups shows how to simulate data from two groups. One sample (with n1=20 observations) is simulated from an N(15, 5) distribution whereas a second (with n2=30 observations) is simulated from an N(16, 5) distribution. The sample means of the two groups are close

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Programming Tips

Rick WicklinAugust 10, 2020 2

4 ways to standardize data in SAS

A common operation in statistical data analysis is to center and scale a numerical variable. This operation is conceptually easy: you subtract the mean of the variable and divide by the variable's standard deviation. Recently, I wanted to perform a slight variation of the usual standardization: Perform a different standardization

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Learn SAS | Programming Tips

Rick WicklinAugust 5, 2020 0

Submatrices of matrices

Have you ever seen the "brain teaser" for children that shows a 4 x 4 grid and asks "how many squares of any size are in this grid?" To solve this problem, the reader must recognize that there are sixteen 1 x 1 squares, nine 2 x 2 squares, four 3 x 3 squares, and one 4 x 4 square.

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