Lists are collections of objects. SAS/IML 14.2 supports lists as a way to store matrices, data tables, and other lists in a single object that you can pass to functions. SAS/IML lists automatically grow if you add new items to them and shrink if you remove items. You can also modify existing items. You can use indices to refer to items of a list, or you can assign names to the items to create a named list.

Create a list

You can create a list by using the ListSetItem subroutine to assign a value to each item:

proc iml;
L = ListCreate(2);                  /* L is two-item list */
call ListSetItem(L, 1, 1:3);        /* 1st item is 1x3 vector */
call ListSetItem(L, 2, {4 3, 2 1}); /* 2nd item is 2x2 matrix */

The arguments for the ListSetItem subroutine are list, index, and value, which is the same order that you use when you assign a value to a matrix element, such as A[2] = 5.

If you do not know how many items the list will contain, or if you later want to add additional items, you can use

X = {3 1 4, 2 5 3}; /* create a 2x3 matrix */ call ListAddItem(L, X); /* add 3rd item; list grows */

Notice that the syntax for the ListAddItem subroutine only requires the list and the value because the new item is always added to the end of the list. At this point, the list contains three items, as shown below:

Insert, modify, and delete list items

A convenient feature of SAS/IML lists is that they automatically resize. You can insert new items into any position in the list. You can also replace an existing item or delete an item. The following statements demonstrate modifying an existing list.

call ListInsertItem(L, 2, -1:1); /* insert new item before item 2; list grows */ call ListSetItem(L, 1, {A B, C D}); /* replace 1st item with 2x2 character matrix */ call ListDeleteItem(L, 3); /* delete 3rd item; list shrinks */

The arguments for k, existing higher-indexed items are also renumbered. (Conceptually, items "move to the left.") After the previous sequence of operations, the list contains the following items:

Create named lists

In the previous section, the list acted like a dynamic array: it stored items that you could access by using indices such as 1, 2, and 3. For some applications, it makes more sense to name the list items and refer to the items by their names rather than their positions. This is similar to "structs" in some languages, where you can refer to members of a struct by name.

For example, suppose a teacher wants to store information about students in her classes. For each student, she might want to store the student's name, class, and test scores. The following statements create a SAS/IML list that has three items named "Name", "Class", and "Scores". The items are then assigned values:

Student = ListCreate({"Name" "Class" "Scores"}); /* create named list with 3 items */ call ListSetItem(Student, "Name", "Ron"); /* set "name" value for student */ call ListSetItem(Student, "Class", "Statistics"); /* set "class" value for student */ Tests = {100 97 94 100 100}; /* test scores */ call ListSetItem(Student, "Scores", Tests); /* set "scores" value for student */

Although you can still use positional indices to access list items ("Ron" is the first item, "Statistics" is the second item, ...), you can also use the name of items. For example, to extract the test scores into a SAS/IML matrix or vector, you can use

s = ListGetItem(Student, "Scores"); /* get test scores from list */

Lists are for storing items, not for computing. You cannot add, subtract, or multiply lists. However, the example shows that you can extract an item into a matrix and subsequently perform algebraic operations on the matrix.

All = ListCreate();                  /* empty list */
call ListAddItem(All, Student);      /* add "Ron" to list */
 
call ListSetItem(Student, "Name", "Karl"); 
call ListSetItem(Student, "Class", "Calculus");
call ListSetItem(Student, "Scores", {90 92 84 70 80});  
call ListAddItem(All, Student);      /* add "Karl" to list */

SAS/IML 14.2 supports lists, which are containers that store other objects. Lists dynamically grow or shrink as necessary. You can index items by their position in the list (using indices) or you can create a named list and reference items by their names. You can use built-in functions to extract items a list or add new items to a list. You can insert, delete, and modify list items. You can represent hierarchical data by using lists of lists. For more information about SAS/IML lists, see the chapter in the SAS/IML documentation. The documentation shows how lists can be used to emulate other data structures, such as stacks, queues, and trees.

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... in finance, text from financial news, social media, and company filings is used to predict asset price movements and study the causal impact of new information. In macroeconomics, text is used to forecast variation in inflation and unemployment, and estimate the effects of policy uncertainty. In media economics, text from news and social media is used to study the drivers and effects of political slant. In industrial organization and marketing, text from advertisements and product reviews is used to study the drivers of consumer decision making. In political economy, text from politicians’ speeches is used to study the dynamics of political agendas and debate.

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Hey! The organization that publishes all those Psychological Science-style papers has scheduled their featured presentations for their next meeting.

Included are:

– That person who slaps the label “terrorists” on people who have the nerve to question their statistical errors.

– One of the people who claimed that women were 20 percentage points were likely to vote for Barack Obama, during a certain time of the month.

– One of the people who claimed that women are three times as likely to wear red, during a certain time of the month.

– The editor of the notorious PPNAS papers on himmicanes, air rage, and ages ending in 9.

– One of the people who claimed, “That a person can, by assuming two simple 1-min poses, embody power and instantly become more powerful has real-world, actionable implications.”

– Yet another researcher who responded to a failed replication without even acknowledging the possibility that their original claims might have been in error.

– The person who claimed, “Barring intentional fraud, every finding is an accurate description of the sample on which it was run.”

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The whole thing looks like a power play. The cargo-cult social psychologists have the power, and they’re going to use it. They’ll show everyone who’s boss. Nobody’s gonna use concerns such as failed replications, lack of face validity, and questionable research practices to push them around!

Talk about going all-in.

All they’re missing are speakers on ESP, beauty and sex ratio, the contagion of obesity, ego depletion, pizza research, 2.9013, and, ummm, whatever Mark Hauser and Diederik Stapel have been up to recently.

Here’s the official line:

The mission of the Association for Psychological Science is to promote, protect, and advance the interests of scientifically oriented psychology in research, application, teaching, and the improvement of human welfare.

I guess that works, as long as you use the following definitions:
“promote” = Ted talks, twitter, and NPR;
“protect” = deflect scientific criticism;
“advance the interests of scientifically oriented psychology” = enhance the power of a few well-situated academic psychologists and their friends.

It’s a guild, man, nuthin but an ivy-covered Chamber of Commerce. Which is fine—restraint of trade is as American as baseball, hot dogs, apple pie, and Chevrolet.

The only trouble is that I’m guessing that the Association for Psychological Science has thousands of members who have no interest in protecting the interests of this particular club. I said it before and I’ll say it again: Psychology is not just a club of academics, and “psychological science” is not just the name of their treehouse.

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Kevin Lewis suggests the above name for pro football’s newest team, after hearing that “The NFL is letting the Oakland Raiders move to Las Vegas, a move once nearly unthinkable due to its opposition to sports gambling.”

Is there anyone good at graphic design who’d like to design a logo? I’m not sure what images would work here. Maybe a couple of dice, some betting slips, . . . ?

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Le Monde mathematical puzzle launched a competition to celebrate its 1000th puzzle! A fairly long-term competition as it runs over the 25 coming puzzles (and hence weeks). Starting with puzzle #1001. Here is the 1000th puzzle, not part of the competition:

Alice & Bob spend five (identical) vouchers in five different shops, each time buying the maximum number of items to get close to the voucher value. In these five shops, they buy sofas at 421 euros each, beds at 347 euros each, kitchen appliances at 289 euros each, tables at 251 euros each and bikes at 211 euros each, respectively. Once the buying frenzy is over, they realise that within a single shop, they would have spent exactly four vouchers for the same products. What is the value of a voucher?

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1. Stan programmer. This is the “Stan programmers” position described here.

2. Stan project development. This is the Stan business developer/grants manager described here.

To apply, click on the first link for each position above (the academicjobs.columbia.edu site) and follow the instructions.

P.S. In first version of this post I messed up the links. They’re fixed now.

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Probability and Statistics in the Study of Voting and Public Opinion

Elections have both uncertainty and variation and hence represent a natural application of probability theory. In addition, opinion polling is a classic statistics problem and is featured in just about every course on the topic. But many common intuitions about probability, statistics, and voting are flawed. Some examples of widely-held but erroneous beliefs: votes should be modeled by the binomial distribution; sampling distributions and standard errors only make sense under random sampling; poll averaging is a simple problem in numerical analysis; survey sampling is a long-settled and boring area of statistics. In this talk, we discuss some challenging problems in probability and statistics that arise from the study of opinion and elections.

I’ll be speaking at the Applied Probability and Risk Seminar, 1:10-2:10pm in 303 Mudd Hall, Columbia University.

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Did you know that you can check a SAS macro variable to see if ODS graphics is enabled? The other day I wanted to write a SAS program that creates a graph only if ODS graphics is enabled. The solution is to check the SYSODSGRAPHICS macro variable, which is automatically updated by the SAS system whenever ODS graphics is enabled or disabled. (Thanks to Warren Kuhfeld for this tip!) The SYSODSGRAPHICS variable has the value 0 for "off" and 1 for "on."

For example, the following SAS/IML program checks to see if ODS graphics is on. If so, it creates a bar chart of a categorical variable. If not, it computes the count for each category and prints a frequency table:

ods graphics on;         /* -OR-  ods graphics off */
proc iml;
use sashelp.cars;  read all var "Origin";  close;
 
if &SYSODSGRAPHICS then  /* is ODS graphics enabled? */
   call bar(Origin);     /* optionally display a graphical summary */
/* always display a tabular summary */
call tabulate(Categories, Counts, Origin);
print Counts[colname=Categories];

The SYSODSGRAPHICS automatic macro variable is a recent addition to the automatic macro variables in SAS. You can read Rick Langston's 2015 paper to discover other (relatively) new macro features in SAS 9.3 and SAS 9.4.

SAS has many other automatic macro variables. In general, you can use automatic macro variables in SAS to check the status of the SAS system at run time. Some of my other favorite automatic macro variables (which some people call system macro variables) are the following:

• SYSERR, SYSERRORTEXT, and SYSWARNINGTEXT: Provide information about errors and warnings from SAS procedures. In my book Statistical Programming with SAS/IML I show how to use these macro variables in conjunction with the SUBMIT/ENDSUBMIT statements in SAS/IML.
• SYSVER and SYSVLONG: Provide information about your version of SAS. You can use these macro variables to execute newer, more efficient, code if the user has a recent version of SAS.
• SYSSCP and SYSSCPL: Provide information about the operating system. For example, is SAS running on Windows or Linux?

Do you have a favorite automatic variable? Leave a comment and tell me how you use automatic variables in your SAS programs.

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