Scientific Computing

If nothing happens on typing ImageJ-Win64.exe

Try typing (once):

ImageJ-Win64 --cp jars/javac.jar

to fix the problem. Thereafter, just click on ImageJ-Win64 to start.

Reference

One day, I suddenly couldn’t SSHFS mount via the head end server from any computer.

• could not ssh into the main head end server
• could ssh into the individual cluster units.
• could not sshfs mount from those cluster units
• could see files via ssh.

Workaround:

Using a Windows guest virtual machine, I was able to mount the windows side of the network share (that I can typically always mount via sshfs) I could sftp and scp from one of the cluster nodes (not the head end node, since I couldn’t get in via ssh).

Probably a weird, incorrect workaround–but it got the badly needed files in a pinch.

SSHFS allows accessing directories and files on remote SSH servers as if they were on your local PC. One quirk is that accessing a large number of small files will incur a speed penalty.

When specifying the remote directory using sshfs, include a trailing slash to avoid Input/Output Error messages.

• correct: sshfs -o workaround=rename joe@server:/opt/netfiles/ ~/Z
• incorrect: sshfs -o workaround=rename joe@server:/opt/netfiles ~/Z

For reliable hamlib connection to the Kenwood TS-2000, make rigctl wait for the TS-2000 to catch up by using the hardware handshake.

rigctl -m 214 -s 57600 -r COM1 -C serial_handshake=Hardware

This solves the intermittent errors with the Kenwood TS-2000 and hamlib like:

read_string(): Timed out 0.2 seconds without reading a character.

Scripts for simple command-line remote control of radios and rotors via hamlib

Lamborghini R485 tractor:

A few quotes from Jay Leno’s Garage:

• Ferrucio Lamborghini said to have originated tractor pulls against dominant brands of tractors like Fiat.
• 12 speed transmission, first gear up to 0.3 mph, 12th gear up to 14 mph.
• Two-footed clutch
• Lamborghini said to have exported fewer than 20 tractors to California, targeted for vineyards and olive groves where low tractor height was valuable.

This is a regular expression string to get YYYY-MM-DD string from arbitrary length string:

(19|20)dd([- /.])(0[1-9]|1[012])2(0[1-9]|[12][0-9]|3[01])

With Matlab/Octave regex for dates works like:

input = '09av8joj23oit2pojiijo/20398/vj89/2012-10-15/0298f9082j23'; %random stuff with date in it

regStr = '(19|20)dd([- /.])(0[1-9]|1[012])2(0[1-9]|[12][0-9]|3[01])';

[startIndex,endIndex] = regexp(input,regStr,'start','end')

myDate = input(startIndex:endIndex);

If Matlab / Octave is giving vertical columns of text from text files, one character per line, just transpose the text:

data = data(:).'

Imagemagick can show a histogram from the command line. Do this with Python for programmatic use.

magick input.jpg histogram:miff:- | magick display miff:-

input.jpg

image in ANY format to display the histogram

Enable Active Mode for an FTP server if unable to list directories in Filezilla or other FTP software.

Make a square-base 2D data pyramid in Matlab, where:

N

number of pixels per side (e.g. 512)

MinVal

minimum data value (e.g. 0)

MaxVal

maximum data value (e.g. 65535)

N = 256;
MinVal = 0;
MaxVal = 2^16 - 1;

data = nan(N);
temp = uint16(MinVal:round((MaxVal-MinVal)/(N/2)):MaxVal);

for i = 1:N/2
  data(i,i:end-i+1) = temp(i);
  data(i:end-i+1,i) = temp(i);
  data(end-i+1,i:end-i+1) = temp(i);
  data(i:end-i+1,end-i+1) = temp(i);
end

figure, mesh(data)

The values at the “base” of the pyramid are zero, and increase linearly on each side to 65,535. This sort of figure might be useful when testing an optical flow algorithm.