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Move beyond spreadsheets to data mining, forecasting, optimization – and more

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Rick WicklinMarch 9, 2011 1

Cuzick's Test for Trend: A case study in translating a MATLAB program into the SAS/IML language

Several times a year, I am contacted by a SAS account manager who tells me that a customer has asked whether it is possible to convert a MATLAB program to the SAS/IML language. Often the customer has an existing MATLAB program and wants to include the computation as part of

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Rick WicklinMarch 7, 2011 4

Need case-insensitive string comparisons? UPCASE!

String comparisons in SAS software are case-sensitive. For example, the uppercase letter "F" and lowercase letter "f" are treated as unique characters. When these two letters represent the same condition (for example, a female patient), the strings need to be handled in a case-insensitive manner, and a SAS programmer might

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Rick WicklinMarch 4, 2011 6

How to use transparency to overcome overplotting

Do you have many points in your scatter plots that overlap each other? If so, your graph exhibits overplotting. Overplotting occurs when many points have similar coordinates. For example, the following scatter plot (which is produced by using the ODS statistical graphics procedure, SGPLOT) displays 12,000 points, many of which

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Rick WicklinMarch 2, 2011 5

The macro loop that vanished: How to simplify your SAS/IML programs

I don't use the SAS macro language very often. Because the SAS/IML language has statements for looping and evaluating expressions, I rarely write a macro function as part of a SAS/IML programs. Oh, sure, I use the %LET statement to define global constants, but I seldom use the %DO and

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Rick WicklinFebruary 28, 2011 0

Simulation and sampling in Las Vegas

If you haven't signed up for SAS Global Forum 2011 in Las Vegas, you'd better get moving: February 28 is the last day for early registration and the discounted hotel prices. You should also sign up for the pre-conference statistical tutorials, which are filling up fast! I was tempted to

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Rick WicklinFebruary 25, 2011 1

Bias and covariance explained to an 11-year-old

I was inspired by Chris Hemedinger's blog posts about his daughter's science fair project. Explaining statistics to a pre-teenager can be a humbling experience. My 11-year-old son likes science. He recently set about trying to measure which of three projectile launchers is the most accurate. I think he wanted to

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Rick WicklinFebruary 23, 2011 2

SAS/IML operations compared with PROC SQL: Part 1

I don't know much about the SQL procedure, but I know that it is powerful. According to the SAS documentation for the SQL procedure, "PROC SQL can perform some of the operations that are provided by the DATA step and the PRINT, SORT, and SUMMARY procedures." Recently, a fellow blogger,

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Rick WicklinFebruary 21, 2011 1

How to build a vector from expressions

If you are a statistical programmer, sooner or later you have to compute a confidence interval. In the SAS/IML language, some beginning programmers struggle with forming a confidence interval. I don't mean that they struggle with the statistics (they know how to compute the relevant quantities), I mean that they

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Rick WicklinFebruary 18, 2011 1

Comedy vs. Drama: A comparative histogram of TV's top earners

The Flowing Data blog posted some data about how much TV actors get paid per episode. About a dozen folks have created various visualizations of the data (see the comments in the Flowing Data blog), several of them very glitzy and fancy. One variable in the data is a categorical

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Rick WicklinFebruary 16, 2011 4

Converting matrix subscripts to indices

Suppose that you want to create a matrix in SAS/IML software that has a special structure, such as a tridiagonal matrix. How do you do it? Or suppose that you want to find elements of a matrix A such that A[i,j] satisfies a certain condition. How do you get the

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