Tuesday, August 30, 2016

SAS ERROR: Cannot load SSL support. on Microsoft Windows

When using SAS with HTTPS or FTPS, which requires SSL/TLS support, you may see this error message in the SAS log.

ERROR: Cannot load SSL support.

Here is an example of code that can trigger the error.

filename myref url "https://www.google.com";
data _null_; 
infile myref; 

The cause was that

Thursday, June 23, 2016

SAS error "insufficient memory" on remote queries with wide rows

SAS can give the error The SAS System stopped processing this step because of insufficient memory when querying a single, wide row from a remote SQL Server. The following code fully demonstrates the problem and shows a workaround. Also, I eliminate the explanation that SAS data sets in general do not support rows this wide.

Wednesday, June 8, 2016

Reusing calculated columns in Netezza and SAS queries

Netezza and SAS allow a query to reference a calculated column by name in the SELECT, WHERE, and ORDER BY clauses. Based on the DRY principle, this reduces code and makes code easier to read and maintain.

Some people call calculated columns derived or computed columns.

In Microsoft SQL Server, SQLite, and other RDBMSs you cannot exactly do this: a workaround is to reference a subquery or view. In Microsoft SQL Server, you can also define a computed column on a table.

Below is an example tested with Netezza 7.2. Notice height_m is used in the SELECT clause, and bmi is used in the WHERE and ORDER BY clauses.

Tuesday, March 15, 2016

In case of error in SAS program, send email and stop

Any automated program should check for errors and unexpected conditions, such as inability to access a resource and presence of invalid values. Unlike traditional programming languages such as Python and C# that stop processing when an error occurs, SAS barrels ahead through the rest of the program. Therefore, carelessly-written SAS programs can create unwanted side effects, such as overwriting an output data set with bad data.

Previously I wrote about a robust solution for checking SAS error codes which wraps the entire program in a macro and invokes %GOTO EXIT in case an error. This is still the ideal solution when some part of the program must continue, but it comes at a cost: wrapping SAS code in a macro disables syntax highlighting in the SAS Enhanced Editor (though not in SAS Studio). Also, it can be awkward to work with the large code block delimited by the macro, so this post focuses on two alternatives.

Thursday, March 10, 2016

R: InternetOpenUrl failed: 'The date in the certificate is invalid or has expired'

Today the two-year-old TLS security certificate for cran.r-project.org expired, so suddenly in R you are getting errors running install.packages or update.packages.

The error looks like this:

> update.packages()
--- Please select a CRAN mirror for use in this session ---
Error in download.file(url, destfile = f, quiet = TRUE) : 
  cannot open URL 'https://cran.r-project.org/CRAN_mirrors.csv'
In addition: Warning message:
In download.file(url, destfile = f, quiet = TRUE) :
  InternetOpenUrl failed: 'The date in the certificate is invalid or has expired'

The workaround is simple: choose another repository! For example:

Monday, February 22, 2016

ISO 3166-1 alpha-2 (two-letter country code) format for SAS

Here is the widely-used ISO 3166-1 alpha-2 format for use in SAS. It is commonly called the two-letter country code format.

The PROC FORMAT code generates a character format, so where the raw data contains a code, such as US, it expands it to the pretty name, such as United States. As with any SAS format, applying the format does not change the underlying data.

Wednesday, February 3, 2016

Undocumented SAS feature: Bulkloading to Netezza with ODBC interface

The SAS/ACCESS Interface to ODBC in SAS 9.4M4 states it supports bulk loading only to "Microsoft SQL Server data on Windows platforms." However, in practice on the Windows platform it also supports bulk loading to Netezza.

Bulk loading is amazingly fast. In some of my benchmarks the duration of the whole bulk loading operation is independent of the number of rows inserted!

By default on Netezza the bulk loading interface delimits values using a pipe character, and for cases where the values contain a pipe, SAS Access Interface to ODBC unofficially supports the BL_DELIMITER option to specify an alternate delimiter. For the ODBC interface, this option is undocumented.

However, there are nuances with the BL_DELIMITER option. According to the SAS Access Interface to Netezza:

Friday, January 29, 2016

Frequency of individual characters from SAS data set

This script counts the frequencies of individual ASCII characters in a single column in a SAS data set and then prints an easy-to-read report.

My initial motivation relates to delimiters. By default bulkloading data from Netezza to SAS (which is very fast) uses the pipe character as a delimiter, but my data set contained values with the pipe character, so this macro identifies alternative delimiters.

Another potential use is cracking a message encrypted using a simple letter substitution cipher.

To begin, this code creates an example data set courtesy of William Shakespeare.