# A Roman Numeral Object, with Arithmetic, Matrices and a Clock

Posted by Cleve Moler,

A MATLAB object for arithmetic with Roman numerals provides an example of object oriented programming. I had originally intended this as my April Fools post, but I got fascinated and decided to make it the subject of a legitimate article.... read more >>

# Bank Format and Metric Socket Wrenches2

Posted by Cleve Moler,

A report about a possible bug in format bank and a visit to a local hardware store made me realize that doing decimal arithmetic with binary floating point numbers is like tightening a European bolt with an American socket wrench.... read more >>

# My Erdös Number and My Trump Number2

Posted by Cleve Moler,

I've long known that my Erdös Number is 3. This means that the length of the path on the graph of academic coauthorship between me and mathematician Paul Erdös is 3. Somewhat to my surprise, I recently discovered that I can also trace a chain of coauthorship to Donald J. Trump. My Trump number is 5.... read more >>

# Morse Code, Binary Trees and Graphs6

Posted by Cleve Moler,

A binary tree is an elegant way to represent and process Morse code. The new MATLAB graph object provides an elegant way to manipulate binary trees. A new app, morse_tree, based on this approach, is now available in version 2.40 of Cleve's Laboratory.... read more >>

# Lake Arrowhead Coauthor Graph Revisited

Posted by Cleve Moler,

The Lake Arrowhead Coauthor Graph came out of the Householder XII conference in 1993 at the UCLA conference center in the mountains north of San Bernardino. John Gilbert now remembers it as one of the first computational social network analyses he had ever seen. Today I revisit it using the new MATLAB graph object.... read more >>

# Patience Chinese Rings Puzzle

Posted by Cleve Moler,

MIT's Professor Daniel Frey recently introduced me to an ancient mechanical puzzle known as "Chinese Rings", "Patience", or "Baguenaudier." I have modified Daniel's simulator to produce a new app. The state space of the puzzle forms a hypercube.... read more >>

# Ulps Plots Reveal Math Function Accuracy2

Posted by Cleve Moler,

"ULP" stands for "unit in the last place." An ulps plot samples a fundamental math function such as $\sin{x}$, or a more esoteric function like a Bessel function. The samples are compared with more accurate values obtained from a higher precision computation. A plot of the accuracy, measured in ulps, reveals valuable information about the underlying algorithms.... read more >>

# Fitting and Extrapolating US Census Data

Posted by Cleve Moler,

A headline in the New York Times at the end of 2016 said "Growth of U.S. Population Is at Slowest Pace Since 1937". This prompted me to revisit an old chestnut about fitting and extrapolating census data. In the process I have added a couple of nonlinear fits, namely the logistic curve and the double exponential Gompertz model.... read more >>

# Season’s Greetings Fractal6

Posted by Cleve Moler,

I don't recall where I found this seasonal fractal. And I can't explain how it works. So please submit a comment if you can shed any light on either of these questions.... read more >>

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