William's Blog

Setting the Axis of a MATLAB Plot

I ran into a situation where I was progromatically making a plot and I wanted it to be formatted correctly each time. This saves me effort from having to manually fix aspects of the plot that aren’t set.

The trouble is, MATLAB doesn’t make this particularly easy. There’s lots of figure handles and such that need to be manipulated. Here’s a code snippet that a) creates a figure b) lets you manually set the axis properties and c) plots data on that axis.

figure(2); % Create figure #2. Note this figure does NOT have an axis associated

		% with it. If you call 'hold on' it WILL create a default axis.

axes1 = axes('Parent',gcf,'YScale','log','YMinorTick','on',...

    'YMinorGrid','on',...

    'YGrid','on',...

    'XGrid','on'); % Creates a semilog axis with logarithmic y-axis, etc.

hold(axes1,'all'); % Prevents subsequent plots from changing the axis property

plot(...,'Parent',axes1);  % Plot data on this new axis. I don't think this is strictly

 % necessary, but can help if you have trouble.

So, there you go. Don’t forget you can use the following to add title, labels, and set the axis limits:

title({'Title line 1','Title line 2'},'FontSize',12);

xlabel('X label','FontSize',12);

ylabel('Y label','FontSize',12);

ylim([1e-012 1]);

xlim([1 10]);

MOG Just Sent Me My Plaintext Password

So there’s plenty of online music streaming services - Pandora, Spotify, Grooveshark … and MOG. MOG just announced their new “free” service so I decided to sign up. Awesome.

All fine and good until I get my confirmation email:

WTF MOG?! You’re storing my password in plaintext?!? Have you ever developed a web app before? Hash-ed much?

Long story short, if you care about security you won’t sign up for MOG.

# mog

# security

Mr. Hamilton could stand to break up some sentences

I’m reading the Federalist Papers. Two paragraphs in, I come across this monster:

The most formidable of the obstacles which the new Constitution will have to encounter may readily be distinguished the obvious interest of a certain class of men in every State to resist all changes which may hazard a diminution of the power, emolument, and consequence of the offices they hold under the State establishments; and the perverted ambition of another class of men, who will either hope to aggrandize themselves by the confusions of their country, or will flatter themselves with fairer prospects of elevation from the subdivision of the empire into several partial confederacies than from its union under one government.

James Madison; Alexander Hamilton; John Jay. The Federalist Papers (Kindle Locations 129-133).

One sentence. Wow.

Anonymous asked

Hey William, I am writing to you to gain some insight on Underwater optics. Its my final year project though research based I do have model the channel modeling in MATLAB. My question is:

Why to Choose a Laser Didoe than a LED as an underwater optical transmitter?

I would higly appreciate a response. Thank you for your time

Regards,
Rohan Kakade
Student at the University of Nottingham, UK
eexrk4"at"nottingham"dot"ac"dot"uk

Rohan,

It’s a complicated set of trade-offs. The biggest decider (in practice so far) seems to be the issue of pointing and tracking. This is (more) easy with a LED (or any diffuse source) than a highly colimated source like a laser. It’s up to the system designer to decide whether they want to spend money/power on better pointing and tracking or generating enough optical power with LEDs to transmit the required distance.

Source coherence seems to play little effect (so far) as the scattering from the channel destroys the coherence. You can check out this paper for more reference: http://www.mendeley.com/research/effects-underwater-turbulence-laser-beam-propagation-coupling-singlemode-optical-fiber-2