1. 2013

    Web Plot Digitizer

    It’s a common task among scientists to have to extract data from a plot when the raw numbers aren’t available. Today I found a webapp that does this the right way: Web Plot Digitizer, by Ankit Rohatgi.

    The complaint I usually have about these digitizer applications is that they’re nonintuitive. Extracting data is fundamentally a simple process: define the coordinate system, then click points and the program tells you their coordinates. And that’s all Web Plot Digitizer does. It even has clearly labeled buttons at each step so that it’s not too hard to figure out what to click when. Most other digitizing programs have a lot of extra buttons which do things that I usually don’t manage to figure out, and they may give them fancy names so that you’re not sure what to click to get to the numbers. But not so with this one. Pretty much all it takes to use the program is shown in this one sequence of screenshots, from the app’s website:

    Next time you’re staring at a plot, give this a look!

  2. 2011

    How much does data weigh in flash memory?

    An interesting article in the New York Times has been making the rounds of the internet lately. It talks about the tiny theoretical increase in weight of a Kindle when its memory is full as opposed to when it’s empty. Since I’ve previously written about the weight of data on a magnetic hard drive, I couldn’t resist taking a look at the equivalent effect for flash memory.

    To begin with, we need to know a little about how flash memory works, and to do that, we need to know how transistors work. A transistor is just a tiny electrical switch. It has two contacts, the source and the drain, that are separated by a layer of material with an excess or lack of electrons. Normally this configuration blocks any current from flowing between the source and the drain. But when the right kind of voltage is applied to the separation layer, it removes the excess (or fills the lack) of electrons, allowing current to pass through. (For the record, I know I’m not doing justice to semiconductor physics here.)

    As described in a pretty good article on Explain That Stuff!, and several other sources I’ve …