GNU Octave Custom Colormap

Hello, Unlikely Reader - 
So I wanted to rescale color 3D plot with a more agreeable set of values.  Octave handles this, but I thought I'd write up how because it isn't an everyday task and I'm sure I'll forget how I did it.


Here's some data plotted with the default colormap:

The plot is fine but the wide range of color was subjectively implying more curvature in the data than I meant to.  Of course that's all subjective but the data was supposed to make a point and the colormap was working against it.  






Here's a 3D view that makes my point better, but 3D views on flat surfaces are harder to interpret; for example, the diagonal "valley" of low spots gets a little lost:



So I built my own lowest to highest Red-Yellow-Green colormap and applied it; here's how.
n_levels = (10-7)/0.1 + 1;  % numbers of interest range from 7 to 10


% build RGB channels from red to yellow:
red2yellow_chRed = linspace(1, 1, n_levels/2);
red2yellow_chGreen = linspace(0, 1, n_levels/2);
red2yellow_chBlue = linspace(0, 0, n_levels/2);

% build RGB channels from yellow to green:

yellow2green_chRed = linspace(1, 0, n_levels/2);
yellow2green_chGreen = linspace(1, 1, n_levels/2);
yellow2green_chBlue = linspace(0, 0, n_levels/2);

% create the colormap by stacking and concatenating the channel vectors::

RYG_colormap = [ ...
[red2yellow_chRed'; yellow2green_chRed'] ...
[red2yellow_chGreen'; yellow2green_chGreen'] ...
[red2yellow_chBlue'; yellow2green_chBlue'] ...
];

% set the colormap

colormap(RYG_colormap);

The plot automatically updates and helps support my point that there's not so much curvature in the data.

If you don't like it, you can easily switch back:

colormap("default");

Or if black and white is better for you, there's a predefined grayscale map:

colormap(gray);

There you go.  Colormaps.   Happy (r)Octave-ing!

- nzvyyx

Shuttleworth Kicks Ballmer's ASS

Thanks to LiLi's Live USB Creator I've got a nice clean A:B comparison of M$ vs Linux.  Today's heavy lifting for the OS was to run a perl script (which worked fine under XP):

My shiny new Windows 7 FAILS:

...while Ubuntu running from a 4Gb LiLi Live USB works just fine, thank you:

Best of all, thanks to LiLi's VirtualBox install, I don't even have to choose between operating systems!  Here's Ubuntu running in a virtual machine hosted by my L7 OS.

Maybe I'll be able to get my job done after all.


- nzvyyx

VNC... high quality & free remote access

Dear Blogspot/Blogger.Com:
Thank you for your wonderful service.  I noticed a sidebar ads pushing a for-pay remote PC access program - which will remain unnamed.  It appears to be a scam to continually charge hapless users for free software.


Dear Reader:
If you need to access computers remotely, look into VNC... you'll probably notice that web searches prioritize non-free programs... caveat emptor!  Those ripoff artists have a lot of time on their hands to bury the high quality, cross-platform free stuff with their own web pages and link overload.


- nzvyyx

... and L7 once again FAILS

Yesterday I had MySQL up and running on my overpriced WindoesNT laptop as provided by MegaCorp Inc.  I logged in/out/in/out both as root and a user.  I pulled in my ginormous database that I had saved from my old burn.  I entered data, set up queries and forms in LibreOffice Base.   All appeared to be working fine.  I was a happy user.


Last night I shut down.  Restart the machine in the morning.... login denied.  No MySQL access.  Denied.  Hopefully I can find a way to get my data back, but regardless that was the last straw and it's official:


I HATE WINDOWS 7.


This is probably due to UAC resetting on a reboot, but no matter what: data loss is unacceptable... and since I can't get to the data, it counts as lost.  No matter what, erratic behavior is frustrating as hell for a user.  This "feature" of resetting UAC on reboots is a built-in frustration.


Next plan is to bring in my cheap-O linux box and do all my real work on it.




- nzvyyx

Connecting Base to MySQL

Notes on getting my Ubuntu machine to connect Base to MySQL:
sudo apt-get install libmyodbc


Then add a couple of config files (thanks, OpenOffice Wiki)

 Let Base know what's up:

Connect!

- nzvyyx

bash to dos to bash (thanks, Git!)

When I installed Git, it gave me several context menus to get the bash prompt.  On my new Win7 machine this makes reaching the bash prompt much easier & faster than finding a windows command line... but wait I can easily get a dos prompt FROM the bash prompt.  Woops, I'm never learning any more Powershell or whatever.  C Ya, Ballmer!


As an entertaining aside it appears that the "7" in Windows 7 is a minor release level.  Ya like I didn't already know it was Vista.

- nzvyyx

Plot Digitizer

If you need to pull data from a graphic, Plot digitizer is for you.  Fairly small memory footprint & intuitive controls, and it's cross-platform (which is a big deal for me these days...)
This might help you get it set up:



sudo mkdir PlotDigitizer
cd PlotDigitizer
wget http://downloads.sourceforge.net/project/plotdigitizer/plotdigitizer/2.5.1/PlotDigitizer_2.5.1_Linux_and_Others.tgz
tar -xvzf PlotDigitizer_2.5.1_Linux_and_Others.tgz


- nzvyyx

Finally a Ubuntu complaint

Aha! Ubuntu doesn't support SciTE.  Bummer.
And it looks like the gtk version that shipped w/Maverick was a little stale, so I couldn't just build my own SciTE per the handy instructions in the README file.  Bummer.


And it was pretty easy to fix... Bummer!


First I got up to speed on GTK:
sudo apt-get install libgtk2.0-dev

Then, following the README included in the SciTE source download, I built Scintilla and then SciTE.  Only catch was I didn't want it installed on my desktop, so I unzipped the files into /usr/local to build & install there.

cd scite227
cd scintilla/gtk
make
cd ../..
cd scite/gtk
make
sudo make install


- nzvyyx

L7 vs Linux

"Computer experts" are a byproduct of the Micro$oft's planned obsolescence business model. 


Micro$oft is a huge company.  They need money or they'll go out of business.  So, every few years they "sell" you another software product.  Maybe the product you were using worked fine... doesn't matter!  They need revenue and the product you already bought isn't generating any cash for them.


From one perspective they didn't really "sell" you anything anyway.  You are pretty much leasing your operating system.  You don't own your copy of Windows; it is licensed to you.  


Anyway, to assure their own perpetuity, every few years they "sell" you something.  It has to be different than their last version or people might suspect they're being scammed.  This process is called "upgrading" rather than "constant churn," which is how I think of it.  


Given that computers are difficult, picky and arcane, this constant churn creates a job position  for people who are good at memorizing lots of detail... voilà, you have invented the computer expert. 


This whole rant was generated by the extreme difference between my work computer Windows7 "upgrade" vs my recent Ubuntu kernel "upgrade..." unlike L7, I have a couple of post-upgrade scripts I run for Ubuntu, one for my wireless chip and this one (if I need it).
Most of my add-ons to ubuntu are handled by looping an apt-get command on an array of package names, but because Canonical doesn't support SciTE my poor little script has to work slightly harder.    


#!/bin/bash


# copy this file to your desktop, 
# and make it executable via sudo chmod +x 
clear
sudo su


declare programs=("chromium-browser" "octave" "gnuplot" "texmaker" "mysql-server" "r-base" "gimp" "gpaint" "scite")


echo "installing ${#programs[*]} programs: ${programs[@]}"


for program in ${programs[@]}
do
  problem=$(dpkg -s $program | grep installed)
  echo Checking $program: $problem
  if [ "" == "$problem" ]; 
  then
    echo "No $program. Setting up $program"
    sudo apt-get install $program 
  else
    echo "$program installed."
  fi
  clear
done


# add headphones
sudo echo "options snd-hda-intel model=thinkpad" >> /etc/modprobe.d/alsa-base.conf


# add scite as default text editor & make visible line numbers
sudo perl -pi.bak -e 's/gedit/scite/g' /usr/share/applications/defaults.list
sudo perl -pi.bak -e 's/\Q#line.margin.visible\E/\Qline.margin.visible\E/g' 



# ubuntu doesn't support scite... this installs scite v2.27
wget http://prdownloads.sourceforge.net/scintilla/scite227.tgz
sudo cp scite227.tgz /usr/local
cd /usr/local
sudo tar -zxvf scite227.tgz
cd scintilla/gtk
sudo make
cd ../..
cd scite/gtk
sudo make
sudo make install

- nzvyyx