One informat to rule them all: Read any date into SAS

If you obtain data from web sites, social media, or other unstandardized data sources, you might not know the form of dates in the data. For example, the US Independence Day might be represented as "04JUL1776", "07/04/1776", "Jul 4, 1776", or "July 4, 1776." Fortunately, the ANYDTDTE informat makes it […]
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Read data into vectors or into a matrix: Which is better?

In the SAS/IML language, you can read data from a SAS data set into a set of vectors (each with their own name) or into a single matrix. Beginning programmers might wonder about the advantages of each approach. When should you read data into vectors? When should you read data […]
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Excluding variables: Read all but one variable into a matrix

Dear Rick, I have a data set with 1,001 numerical variables. One variable is the response, the others are explanatory variable. How can I read the 1,000 explanatory variables into an IML matrix without typing every name? That's a good question. You need to be able to perform two sub-tasks: […]
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Writing data in chunks: Does the chunk size matter?

I often blog about the usefulness of vectorization in the SAS/IML language. A one-sentence summary of vectorization is "execute a small number of statements that each analyze a lot of data." In general, for matrix languages (SAS/IML, MATLAB, R, ...) vectorization is more efficient than the alternative, which is to […]
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Read from one data set and write to another with SAS/IML

Many people know that the SAS/IML language enables you to read data from and write results to multiple SAS data sets. When you open a new data set, it is a good programming practice to close the previous data set. But did you know that you can have two data […]
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Read hundreds of data sets into matrices

Do you have dozens (or even hundreds) of SAS data sets that you want to read into SAS/IML matrices? In a previous blog post, I showed how to iterate over a series of data sets and analyze each one. Inside the loop, I read each data set into a matrix […]
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Read data sets that are specified by an array of names

One of my favorite features of SAS/IML 12.1 (released with 9.3m2) is that the USE and CLOSE statements support reading data set names that are specified in a SAS/IML matrix. The IMLPlus language in SAS/IML Studio has supported this syntax since the early 2000s, so I am pleased that this […]
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Reading special SAS data sets into matrices

SAS has several kinds of special data sets whose contents are organized according to certain conventions. These special data sets are marked with the TYPE= data set attribute. For example, the CORR procedure can create a data set with the TYPE=CORR attribute. You can decipher the structure of the data […]
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Reading big data in the SAS/IML language

A SAS/IML user on a discussion forum was trying to read data into a SAS/IML matrix, but the data was so large that it would not fit into memory. (Recall that SAS/IML matrices are kept in RAM.) After a few questions, it turned out that the user was trying to […]
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Access rows or columns of a matrix by names

Did you know that you can index into SAS/IML matrices by using unique strings that you assign via the MATTRIB statement? The MATTRIB statement associates various attributes to a matrix. Usually, these attributes are only used for printing, but you can also use the ROWNAME= and COLNAME= attributes to subset […]
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