Update: August 28th, 2018

There are several ways to get in touch with me:

  • Email me at University of Leeds. My name is Mike Croucher and the email format is
  • Email my personal address (but you’ll need to do a bit of work to decode it).
  • Post a comment to any page or post on Walking Randomly (This one will do fine for example) and give me your email address – I’ll then reply to you.  I will withhold publication of your comment if you ask me to and I’ll never republish your email address.
  • Say hi to me on Twitter
  • Connect with me on LinkedIn

There are several methods by which you can follow WalkingRandomly.

  1. Raul Gonzalez
    March 13th, 2010 at 03:08
    Reply | Quote | #1

    Hi my name is raul gonzalez
    i am a senior and prom is right around the corner. I would like to know if there is a formula that i can use to spell out “prom”? I have a TI-89 what mode would i have to be in?? I would like to ask my date in a mathematical way since we are both in the same Calculus class and i thought it would be nice for me to ask her this way. Thank you very much and i hope you can help me.

  2. March 13th, 2010 at 13:01
    Reply | Quote | #2

    Hi Raul

    I’ve never used a TI-89 so am not sure what it can or cannot do. If I were you I would try looking into Bézier curves. With a bit of effort you will be able to use these to come up with a set of parametric equations that will spell out letters.

    The following link may be a good start

    Good luck!

  3. Taylor Ralston
    May 12th, 2010 at 23:31
    Reply | Quote | #3


    Love your blog! I actually wasted tons of time I need to be studying for midterms on the spiral circle post a while ago (it was fun though). I need your help. I use Mathematica 7, and I have am using it to analyze experimental data. I need to export the Plots and Manipulate objects I construct to a SWF or FLV format. I’ve tried using the Export command, but unfortunately the output file is not dynamic! Mathematica renders each animation frame by frame (even if a slider is present in the Manipulate object). What I’d like is to create a 3D plot and Manipulate objects, export them to SWF and put them on a website so people can interact with it: rotate the 3d plots, and change the sliders in the manipulate objects. Is there any way (or workaround) for this? This would totally revolutionize the dissemination of analysis results!


  4. May 15th, 2010 at 17:37
    Reply | Quote | #4

    Hi Taylor

    You can’t do that at the moment I’m afraid and I don’t expect that to change in the near future. You might be able to do what you want with Web Mathematica but that’s a whole different ball game

    I’ve no experience with Web Mathematica myself so can’t offer any further advice at the moment.

    Best Wishes,

  5. August 16th, 2010 at 16:43
    Reply | Quote | #5


    You seem to have enjoyed du Sautoy’s “The Music of the Primes”, so you may well be interested in my new one (volume 1 of a trilogy):

    This book has a significantly different emphasis from that of du Sautoy (and the three other books about the Riemann Hypothesis that came out around the same time. It’s concerned solely with *what is known* rather than *how we came to know it* (which has been adequately explored elsewhere). The Riemann Hypothesis will not appear until Volume 2.

    Volume 1 ends having demonstrated to the reader, in wholly visual terms, how the system of positive integers can be (in a sense) harmonically decomposed, as discovered by Riemann in the 1850s. It has always struck me as odd that this truly remarkable fact is not generally taught as part of undergraduate mathematics curricula, and many (quite possibly a great majority of) professional mathematicians outside number theory seem unaware, or only vaguely aware, of it. But I believe that I’ve succeeded in explaining it in a way that anyone with a basic level of intelligence and focus can understand.

    Robert Fuller (former Columbia University physicist, author of the seminal text book “Mathematics for Classical and Quantum Physics”) has described it as a “pedagogical tour de force” (and “clearer than du Sautoy”). Brian Josephson (Cambridge Nobel physics laureate) has responded to the book with similar enthusiasm, both scientists having expressed an eagerness to read the next two volumes.

    keep blogging!

  6. August 16th, 2010 at 18:09
    Reply | Quote | #6

    Hi Matthew,

    Thanks for the comment. Looks like a good book – I’ll add it to the list of things to read.


  7. Abdulhaq
    September 12th, 2010 at 18:38
    Reply | Quote | #7

    Hey Mike

    First of all, I love your blog ;)

    I have been facing a problem with MATLAB and MAPLE and because it’s a small problem I couldn’t find a solution anywhere. I thought Mike Croucher the owner of one the most wonderful blogs will definitely help.

    As you know, Maple 14 comes with the Maple Toolbox for Matlab, I have Maple 14 and Matlab 2010b. When installing Maple 14, I got to choose the default symbolic engine for Matlab and I choose Maple. It’s stated in the installation that I could always change the default symbolic engine by following the instructions in ‘help matlab_symbolic’.

    I think I followed the instructions, here are bits of it:

    [QUOTE] MATLAB_SYMBOLIC – Setting the default symbolic toolbox
    The default symbolic toolbox is the version of the symbolic toolbox
    used by MATLAB when it is launched using the standard start scripts or
    shortcuts. The default symbolic toolbox is determined by the
    environment variable
    which must be set to either ‘maple’ or ‘matlab’. To change
    the default, set the variable to the appropriate value:
    maple to use the Maple Toolbox;
    matlab to use The MathWorks (Extended) Symbolic Math Toolbox.[/QUOTE]

    I’m not an old user of Matlab nor am I a new user, but the simplicity of the above instructions and the fact I couldn’t change the engine made feel like a total ‘noob’

    What I understood is that matlab_symbolic is a variable and needs to be changed as I want, just the same as saying x = ‘matlab’ or x = ‘maple’. This didn’t work, I tried matlab_symbolic = ‘matlab’ and nothing changed (tried it in capital letters as well, I figured that the engine did not change because of the way Maple engine outputs data). In addition, the ‘symengine’ function does not work any more in recent versions.

    Can you please help me in changing symbolic engines? What am I missing?

    Keep posting great topics in your blog :top:



  8. Danielle
    December 8th, 2010 at 23:10
    Reply | Quote | #8

    Hi Mike,

    Just thought you would want to let everyone know about the Mr. Wizard DVD’s for a great holiday gift. I lovee them and wanted to share that with you, maybe you can write something up about it. is doing a great holiday promotion to for all those Mr. Wizard fans out there, like myself.


  9. Martin Cohen
    August 15th, 2011 at 23:36
    Reply | Quote | #9

    Archimedes Method – from an article in NA Digest

  10. Georgie
    September 25th, 2011 at 18:22

    Have you any idea what the wonderful book is where Heisenberg writes of walking in the mountains and thinking? I read it at 17 and would love to find it again. Thanks.

  11. September 25th, 2011 at 22:28

    @Georgie I wonder if it would be this one? Physics and Beyond:Encounters and conversations

    Google Books will let you view limited snippets. I searched for mountain walking within it..hopefully this link will work:

    Look familiar?


  12. August 16th, 2012 at 14:52

    Hi Mike,
    I have been working on Maxima on Android porting. Recently I uploaded my first APK to the Google play.

    I would be happy if you pick it up in your next monthly math software introduction article.

    Thanks and best regards,
    Yasuaki Honda

  13. August 19th, 2012 at 18:37

    Hi Yasuaki

    I look forward to playing with it. Will definitely mention it on the next month of math software.


  14. Lawrence
    November 3rd, 2012 at 19:50

    Thought you might want to include a short note in your Month of Math Software to let python programmers know there is a package Svgwrite a good way to create Scalable Vector Graphics which are viewable with any modern uptodate browser. The free, independent SVG standard is not specifically aimed at mathematics but at the base are vectors so translation, rotation, scaling and zooming is all included. I’ve create example python programs and svg are at
    which show Bezier curves, tiling, guilloches and Perlin noise. Internet Explorer 9 will not show the feTurbulence filter so Windows 7 users will need to use another browser or wait until Microsloth decides to service existing users. IE10 was announced April 2011 but has not yet been released for Windows 7. It is used in Windows 8.
    – Lawrence

  15. November 21st, 2012 at 06:58

    Hi Mike

    I’ve been following your blog for more than a year now and find it very insightful. Since I don’t work with math software on a daily basis I really enjoy your “Month of Math Software” updates every month as they keep me up to date of what is going on out there.

    My day job involves firmware and hardware development and I’ve identified a problem with the EDA industry: The tools used produces and use a wide range of files which are not properly classified anywhere. There are numerous reasons for this, but I won’t go into that now. To solve the problem I’ve created a repository on GitHub which attempts to use the power of the crowd to properly classify these files. There are many advantages of have these files properly classified (referencing them, version control, documenting code etc.)

    After I created the repository I noticed an overlap in the EDA and math software fields since some of the firmware development work I do is done in Simulink, and then generated into VHDL by Xilinx System generator.

    I decided to add a math software section to this repository where the same thing can be done for the many math tools out there. The math software list is almost empty at the moment but its a starting point for people out there who uses math software on a daily basis.

    The repository is hosted here:

    I thought that you might find this interesting,

  16. November 21st, 2012 at 10:56

    Thanks Jaco

  17. David Sweeney
    March 13th, 2013 at 13:02

    Have you discovered ‘J’ programming on the iPad? Its a revised implementation of APL without the funny characters. I found it in the Apple app store while looking for programming languages. Looks good for matrix operations.

  18. March 14th, 2013 at 15:36

    Sounds great, I’ll take a look,

  19. May 8th, 2013 at 22:36

    Hi –
    I’m curious – some time ago on you mentioned that matlab’s tic and toc often has variance even for the same operations. This never irked me, as it seems somewhat obvious, given operating system overhead and random factors, but it just occurred to me that the variation is really quite large…typically by, say 100 ms or so. Even a standard deviation of 10 ms seems kind of large. I’m keen to know what other factors come into play, if you have some thoughts.


  20. Jaqueline
    June 13th, 2014 at 17:50

    My code makes 500 simulation runs, each one generating 1000 observations of the variable of interest. It makes use of trnd, rand and randperm with rng(sd,’twister’). The problem is that I am getting explosive results of the variable of interest. Do you have an idea of what is wrong?


  21. June 23rd, 2014 at 05:03

    I would like to submit a digital non-deterministic random bit generator for your evaluation –

  22. Max
    July 23rd, 2014 at 08:07

    Dear Mike,

    Amazing Blog with examples and explainations which have helped me a lot over the years. I moving from matlab to python.

    I ran into a little problem and was wondering if you knew anything about this.
    My matlab code is using lsqnonlin with a predetermined jacobian and l-m algorithm to fit a function. I normally get a straight line out of it. Trying to move the code to python to save on that licensing fee, I am using leastsq from scipy. But this returns a log function fit. I was wondering if you have encountered something like this yourself. Is there a way to make leastsq behave like lsqnonlin?

    Thanks in advance for any help! I hope this blog keeps active for a long time. Such a wealth of neat little tricks and good explanations!

  23. June 4th, 2015 at 05:15

    Just curious, have you tried your Mathematica on Raspberry tests with the new Raspberry Pi2?

    I’m looking at getting a Pi to learn Mathematica for a cryptographic application. I thought I could do it using VisualBasic but it crackups on me. I need to calculate the factorial of more than 4 million, then multiply it by other similarly large numbers. Even with BigIntegers, VB chokes on 2048! thinking it’s infinity and BigFloats don’t work at all.

    I could use Mathematica on my PC, but have been so frustrated by this and other computer based project that I won’t buy ANYTHING until I KNOW it works. IF I had enough graph paper, it’d probably be more successful with a pencil!

    Thanks, David

  24. June 4th, 2015 at 05:16

    @David Morton
    Oops, I missed the tick box about notify me by email…

  25. Mike Croucher
    June 4th, 2015 at 10:34

    Hi David

    I haven’t tried Mathematica on the Pi 2 yet. I expect it should be about to handle the factorial of 4 million. Mathematica on my Mac calculated it in a few seconds, all 24,671,066 digits of it :)


  26. Dean
    September 24th, 2015 at 15:54

    Hi Mike,

    Thanks for the talk earlier today, I really enjoyed it.

    Here is a link to the Github project I mentioned (that can turn a Jupyter Notebook into a slideshow):


  27. Karen McCarty
    September 28th, 2015 at 02:12

    Okay Mike, I am probably not your typical commenter. I am. Psychotherapist in Atlanta, GA. Lately, I have been experimenting with what I call “curly walking”. It occurred to me one day how different my energy is when I shift from linear to non-linear walking. I am imagining it gets me out of the left hemisphere into the right hemisphere. It is novel,,which the right hemisphere loves and it feels much more playful and less tense…all things I would like to increase in my life and in my clients’ lives. So I googled anything that described non-linear walking and you were pretty much the only site close to this idea. I am no scientist but I have always been attracted to Chaos Theory ever since I read the book Chaos. It certainly is much more fun getting there curly.

  28. Lian Shen
    February 26th, 2016 at 23:55

    Hi Mike,
    do you know if NAG’s Mersenne-Twister random number generate produces same sequence in 32bit and 64bit Matlab?

    As I read from, the outputs of 64bit version is totally different to the 32bit one.


  29. John Cremona
    September 2nd, 2016 at 20:38

    Your item about spreadsheets changing gene names rang a bell with me: earlier today I had to enter my bank account number and sort code into a spreadsheet (excel but I was using libreoffice) and it converted ??-01-28 into the date ??/01/2018. That could have cost me money if I had not noticed and reentered it without the dashes.

  30. Victor
    October 11th, 2016 at 13:37

    Hi Mike

    Thanks for the guide installing Environment-Modules.

    Do you have any reference I can follow in order to install mpich and openmpi as loadable modules in Ubuntu?

    I saw that I can download the list of needed packages for each one of them from Synaptic, I will try to download them by myself, configure them with prefix and make-install them creating successive modules until I can create each module. Do you think that it will be a successful procedure?



  31. Mike Croucher
    October 13th, 2016 at 08:29

    Hi Victor

    For OpenMPI, you might find the notes I made for Sheffield’s HPC service useful. Includes install script and modulefile for our system.

    It’s for a redhat based system for I don’t think that should matter too much.


  32. Victor
    October 15th, 2016 at 13:14

    @Mike Croucher
    Hi Mike,

    Unfortunately, the links in the page you sent me are not working. I will try again later… perhaps…

    Do you think that if I install MPICH outside of environmental modules and later OPENMPI within env-mod, Y will be able to run the system without one ore the other just loading or unloading OPENMPI?



  33. Mike Croucher
    October 17th, 2016 at 08:30

    Sorry about the broken links — was due to a recent reorganisation. Fixed now.

    I don’t know about your second question.

  34. MySchizoBuddy
    November 29th, 2016 at 23:46

    Wanted to bring to your attention about a new mathcad alternative called Redcrab Calculator

  35. HothGirl
    September 15th, 2017 at 17:13

    I love sagemath. But how does one plot variables? As in if you would like to plot a fourier sine series for some function and you wanted the y line to be evaluated for L or L/2 or L/3 ? I don’t just want the axis to be labeled ‘L/3’ I want sage math to show me the evaluation for the variable L, or L/2, etc.??

  36. Chloe
    October 29th, 2018 at 07:11

    Dear Mike,

    I am starting a PhD in stability analysis of power systems at Manchester and I am using a code that only works with the free trial of the MATLAB Statistics Toolbox. I have tried to download free versions of mvnrnd.m but they give error messages and I’m sure it is just mvnrnd.m that causes the problem. The code also uses gamrnd.m but I think I have found a similar free version of this that works. I work on a Mac at home. Please could you help me?

    Thank you,