Computing

Virtual reality pioneer Jaron Lanier writes in his book You Are Not a Gadget about the lack of creativity in our use of computing power.

Let’s suppose that back in the 1980s I had said, “In a quarter century, when the digital revolution has made great progress and computer chips are millions of times faster than they are now, humanity will finally win the prize of being able to write a new encyclopedia and a new version of UNIX!” It would have sounded utterly pathetic.

The quote specifically alludes to Wikipedia and Linux, but Lanier is critical of web culture in general. I’m not sure what I think about his position, but at a minimum he provides a counterbalance to the people who speak about the web in messianic tones.

Depending on your expectations, you may have different reactions to the statistical function support in Excel. If you expect anything similar to a statistical package, you’ll be sorely disappointed. But if you think of Excel as a spreadsheet for everybody that sometimes lets you do statistical tasks right there without having to open up a statistical package, you’ll be pleased.

I was looking into the functions in Excel 2007 while preparing for a class I taught yesterday. I wanted to emphasize that certain functions are everywhere, not only in mathematical packages like Mathematica and R, but also in Python and even Excel.

Excel’s set of functions is inconsistent, both in the functionality provided and in the names it uses. Having an asymmetric API makes it harder to remember what is available and how to use it. On the other hand, the most commonly needed functions are available. The functions are individually reasonable even though they do not fit together into a simple pattern.

For details, see my notes Probability distributions in Excel 2007.

I discovered along the way that Excel has a GAMMALN function to compute the logarithm of the Gamma function Γ(x). This is a very useful function to have, even more useful than the Gamma function itself for reasons explained here.

Related links:

Comparison of data analysis packages from Brendan O’Connor

R, Excel, and the Windows clipboard (good tips in the comments)

Here are ten things about numerical linear algebra that you may find surprising if you’re not familiar with the field.

1. Numerical linear algebra applies very advanced mathematics to solve problems that can be stated with high school mathematics.
2. Practical applications often require solving enormous systems of equations, millions or even billions of variables.
3. The heart of Google is an enormous linear algebra problem. PageRank is essentially an eigenvalue problem.
4. The efficiency of solving very large systems of equations has benefited at least as much from advances in algorithms as from Moore’s law.
5. Many practical problems — optimization, differential equations, signal processing, etc. — boil down to solving linear systems, even when the original problems are non-linear. Finite element software, for example, spends nearly all its time solving linear equations.
6. A system of a million equations can sometimes be solved on an ordinary PC in under a millisecond, depending on the structure of the equations.
7. Iterative methods, methods that in theory require an infinite number of steps to solve a problem, are often faster and more accurate than direct methods, methods that in theory produce an exact answer in a finite number of steps.
8. There are many theorems bounding the error in solutions produced on real computers. That is, the theorems don’t just bound the error from hypothetical calculations carried out in exact arithmetic but bound the error from arithmetic as carried out in floating point arithmetic on computer hardware.
9. It is hardly ever necessary to compute the inverse of a matrix.
10. There is remarkably mature software for numerical linear algebra. Brilliant people have worked on this software for many years.

Related posts:

Don’t invert that matrix
Searching for John Francis
Applying PageRank to biology
Matrix cookbook
What is the cosine of a matrix?

Microsoft’s Solver Foundation is a numerical optimization library capable of solving problems involving millions of variables and millions of constraints. When I listened Scott Hanselman interview Nathan Brixius from Microsoft’s Solver Foundation team, I expected Brixius to say that Solver Foundation was written in C++ at its core and had a thin C# veneer to make it callable from .NET applications. Instead, he said that Solver Foundation is entirely written in managed code.

Even in heavy-duty numerical code the bottlenecks may not be numerical. The inner loops of the software would execute faster if they were written in C++, but Solver Foundation solves optimization problems about as quickly as other packages written in lower-level languages.

One of the major design goals for Microsoft Office 2007 was making features easier to discover. A study had shown that about 90% of the feature requests for Microsoft Office were for features already in the product. People just didn’t know what was already there.

A major part of Microsoft’s response was the “ribbon” interface. More controls are on display rather than being hidden behind a deep hierarchy of menus. According to Katherine Murray, the user interface changes achieved their goal.

Data is showing that the redesign of Office really did reach this goal — Word 2007 and Excel 2007 users are now using four times as many features as they used in previous versions, and for PowerPoint, the increase in feature use is a factor of five.

The quote above was taken from First Look: Microsoft Office 2010. I’d like to see more details, but the book is a sales brochure and not a statistical report. Still, if you take these figures at face value, it seems the ribbon and other user interface changes were very successful.

Many pundits hate the ribbon. But most of the 500 million people who use Microsoft Office are not pundits.

The Windows File Explorer has a number of keyboard shortcuts that do not apply to Windows programs in general.

First of all, you can type Windows key-E to open the File Explorer. You can close it by typing Alt-F4.

[click to continue...]

A list of dumb things to check when troubleshooting computer problems from Tom Limoncelli, author of Time Management for System Administrators. A few examples:

• Make sure CapsLock is off. (Same for ScrollLock and NumLock)
• Are both ends of the (power/network/video/etc.) cable plugged in?
• Use cut-and-paste to copy that variable name to see if it was entered correctly.

Listen to an interview with Tom Limoncelli from the StackOverflow podcast.

This weekend I ran across a post by Shaun Boyd called Ten reasons it doesn’t pay to be the computer guy. He begins with the observation that if you’re “the computer guy,” most of your accomplishments are invisible. Nobody consciously notices things working smoothly. In fact, if you do a great job of preventing problems, people will assume you’re not needed. After discussing being unappreciated, Boyd goes on to complain about unreasonably high expectations people have of  “the computer guy.”

These are valid complaints. However, they somewhat offset each other. Yes, much computer support work is invisible, but the firefighting aspects of the job are very visible and often appreciated. Other computer careers are less visible than desktop support and do not have the same potential for positive client interaction. Security may be the worst. Nobody ever notices the lack of security problems. The only potential visibility is negative.

I think the problem is not so much a lack of visibility but a natural incentive to concentrate on the more visible aspects of the job. It’s natural to do more of what is rewarded and less of what is ignored. Troubleshooting is often immediately rewarded by the gratitude of clients. (”My computer was all messed up and you saved me. Thank you, computer guy!”) Preventative maintenance and infrastructure improvements are appreciated only in the long term, if ever.

These challenges are not unique to computer careers; cure is usually more appreciated than prevention. The other problems Boyd lists are not unique to computer careers either. For example, he mentions the lack of appreciation for specialization.

There is no common understanding that there are smaller divisions within the computer industry, and that the computer guy cannot be an expert in all areas.

Every industry has its specializations, though specializations within the computer industry may be less widely known. Maybe specializations are harder to appreciate in newer industries; not long ago the computer guy could be an expert in more areas. Another difficulty is that computers are mysterious to most people. They find it easier to imagine why there are different kinds of doctors for eyes and ears than why there are different kinds of computer guys for desktops and servers.

Boyd makes one point that is almost unique to the computer industry: rapid change devalues skills. Every industry experiences change, but few change at the same rate as the computer industry.

Thanks to the constantly declining price of new computers, the computer guy cannot charge labor sums without a dispute. … desktop computers are always getting smaller, faster, and cheaper. It’s possible to purchase a new desktop computer for under $400. If the computer guy spends five hours fixing a computer and wants $100/hour for his time, his customer will be outraged, exclaiming “I didn’t even spend this much to BUY the computer, why should I pay this much just to FIX it?”

When people in other professions complain about how their jobs are changing, they’re usually complaining directly or indirectly about the impact of computer technology. But the rate of change for those who use a technology is usually less than the rate of change for those who produce and support it.

Related posts:

Rules for computing happiness
Do you really want to be indispensable?
Why there will always be programmers

Microsoft Office 2007 documents are zipped XML files. For example, you can change a Word document’s extension from .docx to .zip and unzip it. Apparently this isn’t widely known; most people I talk to are surprised when I mention this.

I’ve found a couple uses for the zip/XML format. One is that you can unzip a document and grab all the embedded content. For example, .jpeg images are simply files that are zipped up into the Office document.

Another use is that you can crack open a document’s underlying XML to search for something you can’t find via the user interface. You can unzip Office documents, tweak them, and zip them back up. I don’t  recommend this, but I’ve done it when I was desperate. (Microsoft publishes an API for manipulating Office files. Using the official APIs is safer and in the long run easier, but I haven’t looked into it.)

Related posts:

I owe Microsoft Word an apology
Contrasting Microsoft Word and LaTeX

Why would you not want to use your mouse? Some tasks are most efficiently done with a mouse, but others can be done more efficiently with the keyboard.The problem isn’t so much using a mouse versus using a keyboard but rather the time it takes to switch between the two modes. Particularly when using a laptop with a touchpad, it’s faster to use the keyboard.

Why does it even matter? So what if you save a few seconds here and there? It’s a matter of keeping up with your thoughts. Suppose some series of tasks takes 20 seconds with a mouse but you can accomplish the same tasks in 12 seconds using the keyboard. The big deal isn’t that you’ve saved 8 seconds; the big deal is that you’re more likely to finish your tasks before you lose the thought that motivated them.

The same could be said for learning to type more quickly. Typing 20% faster doesn’t directly make you 20% more productive unless you’re a professional typist. The benefit is that your fingers can come closer to keeping up with your brain.

If you’d like to get in the habit of using your keyboard more and your mouse less, you may find this helpful. I’ve created a Twitter account for posting one tip per day on using Windows without a mouse. If you’d like to follow using Twitter, it’s @SansMouse. If you don’t use Twitter, you could subscribe via RSS. I’ve written a few dozen tips so far and they’re in a queue to be dribbled one per day. You could practice one simple tip per day until it is natural to use your mouse much less.

I use my mouse fairly often, though I’m trying to get into the habit of using it less. I’ve recently become persuaded that it’s worthwhile to use the keyboard more and that it doesn’t take that much effort.

Related post:

Four patterns in Windows keyboard shortcuts

How can you delete pages from a PDF file if you don’t have Adobe Acrobat?

Download PDFCreator from SourceForge. It installs as a printer. It lets you create PDFs from any application by selecting PDFCreator as your “printer.” To delete pages from an existing PDF, open the PDF in Adobe Reader and print to PDFCreator the pages you don’t want to delete.

I don’t have a lot of experience with PDFCreator; I just downloaded it today. But it looks good and it worked well for what I was trying to do.

Update: I tried pdftk, recommended in the comments, and it works well. It’s a command line program with more features than PDFCreator.

Here are four patterns for organizing the most common keyboard shortcuts for Windows. First I’ll list the patterns, then I’ll give some qualifications and elaborate on the patterns.

1. Keyboard shortcuts involving letters are all of the form Control-<letter> or Windows-<letter>.
2. The letters used in Control shortcuts and Windows shortcuts don’t overlap.
3. Control in combination with navigation keys moves the cursor. Shift in combination with navigation keys makes a selection.
4. The Tab key cycles through things. What the key cycles through depends on what it is paired with.

When I say Control-<letter> I refer to shortcuts such as Control-C, holding down the Control key and pressing C in order to copy something. When I say Windows-<letter> I refer to holding down the Windows logo key in and pressing some letter.

My goal here is to stick to the most common shortcuts, ones that work across several versions of Windows and with many applications. Also, I’m not including any accessibility sequences such as sticky keys etc.

Control key with letters

Here are the common Windows keyboard shortcuts of the form Control key followed by a letter.

Windows key with letters

Here are the common shortcuts using the Windows key with a letter.

Exceptions

There is one common shortcut that uses a letter and more than just the Control key or Windows key: the combination Windows-Shift-M maximizes all minimized windows. But there are no common shortcuts of the form Alt-<letter> or Control-Shift-<letter> etc.

F is the only letter used with both the Control key and the Windows key. In both cases the command finds something. Control-F finds text within a file and Windows-F searches across directories.

Navigation keys

All the navigation key shortcuts come in pairs.

Control-Home moves the cursor to the top of a document; Control-End moves the cursor to the end.

Control-Left Arrow moves the cursor to the left one word; Control-Right Arrow moves the cursor to the right one word.

Control-Up Arrow moves the cursor up a paragraph; Control-Down Arrow moves the cursor down a paragraph.

Control-Shift-Home selects from the top of the document to the cursor location; Control-Shift-End selects from the current location to the bottom of the document.

Control-Shift-Left Arrow selects one word to the left; Control-Shift-Right Arrow selects one word to the right.

Shift-Left-Arrow expands the selection one character to the left; Shift-Right-Arrow expands the selection one character to the right.

Shift-Up-Arrow selects one line up; Shift-Down-Arrow selects one line down.

Tabbing

The Tab key alone moves the focus in a window, cycling through the controls in the order specified by the application.

Control-Tab cycles through tabs or through windows in an application with multiple windows.

Alt-Tab cycles through running applications.

Windows-Tab cycles through the Task Bar.

Adding the Shift key to any of the above key reverses the cycle order. For example, Alt-Shift-Tab cycles through applications in the opposite order of Alt-Tab.

Miscellaneous shortcuts

Most common Windows keyboard shortcuts are listed above. However, there are several shortcuts that are commonly used but do not fall into a regular pattern. Some of these shortcuts are listed below.

• Shift-F10 brings up a properties dialog, just like right-clicking.
• Shift-Delete permanently deletes a file, bypassing the recycle bin.
• Alt-F4 closes the active window or opens the shutdown dialog if there is no active window.
• Alt-Down Arrow opens a drop down list box.
• Alt-Print Screen grabs an image of the active window rather than the entire screen.
• Alt-Space opens the current window’s system menu.
• Windows-Pause brings up the System Properties dialog.

Most of the function keys are not used often. The most commonly used function keys are

• F1 to bring up help,
• F5 to refresh, and
• F10 to activate an application’s menu bar.

Related posts:
Using Windows without a mouse
Three ways to enter Unicode characters in Windows
Readable path listings
Integrating the clipboard and the command line

I was asking about backup software for Windows the other day and a couple people recommended Cobian Backup. It’s simple to use, but also very configurable. And it’s free.

You can have the software simply copy files or you can have it zip the output (.zip or .7z format). In either case, you don’t need the backup software in order to restore your files.

The software has all the features you’d expect. You can perform full, incremental, or differential backups. You can run backups manually or as scheduled tasks. Etc.

The open source community has a saying: With enough eyes, all bugs are shallow. When enough people look at a piece of code, someone is going find and fix the bugs.

A related principle is that with enough users, all bugs will be reported. With enough people use the software, someone else is going to run into the problem. Someone will report it. Someone will talk about it in an online forum. Someone will blog about it and post a work-around until the bug is fixed. This principle deserves more attention; it’s not cited as often as the shallow bugs principle.

Ideally, you want to use software with lots of eyes and lots of users. Firefox is an open source product with lots eyes and lots of users. But more often you have to pick eyes or users. You have to choose between open but obscure software and closed but popular software. Open source projects may have more people looking at the source code, and so they have the  “many eyes make shallow bugs” maxim working for them. But the user base for many open source projects is tiny compared to their commercial counterparts. The number of users to find and report bugs is small, and the number who document fixes and work-arounds is even smaller.

I’m not ideologically attached to open source or commercial software. I use both. I just want my software to work. And when it doesn’t work, I want to find a solution quickly.

Related posts:

Software profitability in the middle
Software that gets used