typodupeerror

## Comment: Modelling (Score 1)10671067

I work as a mathematical epidemiologist, modelling disease spread in populations. In my work there are three cases when I encounter divide by zero.

1) Disease transmission. Say you have two types of individual, susceptible and infectious, the numbers of which are given by S(t) and I(t), and the total population size is N=S+I. Diseases typically transmits at a rate beta*S*I/N, where beta is the transmission coefficient. What happens when N=0? In this case we want the transmission rate to also be 0.

2) Poisson distributed random numbers. When events happen randomly at rate lambda, the number of events that occur in a time interval dt is n~Poisson(lambda*dt). When lambda=0, you'd always expect n=0. Strictly speaking the Poisson distribution isn't defined for lambda=0, but the limit as lambda->0 is indeed 0. The GNU Scientific Library, Octave, Matlab, and R all return 0 for Poisson(0), however Julia and Numpy both return an error.

3) Adaptive tau leaping. If you aren't using fixed tau leaping, then you need to work out how big a time step you can safely take, which requires bounding the relative change in a variable. This is done by dividing the variable size by the expected change in that variable, and finding the time step tau, repeating for every variable, and taking the smallest time step you get. In this case, it is entirely possible that the expected time step is zero, say when the population is at equilibrium. This doesn't mean that nothing is happening (you should also check that the variance is bounded), and so here you absolutely need that divide by zero is infinity, and that infinity is greater than any other number you might find.

The first two cases are actually undefined (0/0 is mathematically undefined, since you get different answers depending on how you approach the limit), but the desired outcome is clearly zero. The third case is either 0/0 or x/0, but either way you definitely want to interpret the result as infinity.

In my situation, I just wrote a small function called div0, which I use whenever I expect a divide by zero to occur, and know that I want to interpret that as zero, not infinity.

## Comment: Re:Meh (Score 1)830830

As a mathematician and scientist living in Scotland, I lament our use of decimal. Counting in base-12 would have been considerably more useful. Frankly I think we divide by 5 far less often than we divide by 2, 3, 4, or 6, and only one of those gives a round number in decimal. As for the convenience of having 10 fingers, we also have 12 finger segments, allowing us to count to 144 (100 in base 12) on our fingers.

But then imperial measurements are often not based on units of 12. There may be 12 inches in a foot, there are 3 feet in a yard, 16 ounces in a pound, 14 pounds in a stone, 20 ounces in a pint, 8 pints in a gallon, gods know how many feet in a mile, 3 miles in a league... and I only know a few of those without looking them up.

Really, basing everything around one number is such a convenience, even if those numbers aren't always wholly convenient for having day-to-day things ending up in integer numbers.

## Comment: Re:Edgar Matias saved the ALPS switch industry (Score 1)147147

I use Cherry MX browns at work, and MX blues at home. I hugely prefer the blues. The audible click is satisfying, but the tactile feel is just so much better. I haven't tried MX clears yet (strongly tactile, quiet), but I think they would be better off for my work keyboard.

## Comment: When people aren't used to seeing extensions (Score 4, Interesting)564564

Whenever I see a Windows desktop with file extensions disabled, I always try to explain to the person that they should be switched back on, and most people are quite happy to do so (they only had them off because that was the default).

However I was quite dismayed when I looked at my mother's laptop (which I had installed Linux Mint on for her), and she had no file extensions either. It turned out that she thought they looked untidy, and had gone through and manually removed the extensions from every single file in her home directory!

Fortunately the file and mmv commands made short work of fixing this, but I was surprised to say the least.

## Comment: I don't own a TV (Score 1)244244

I haven't owned one since I came to university in 1999. I've had flatmates who've owned one, and I've watched DVDs on my computer, so I haven't been completely free from television. Mostly free from ads though!

Actually I know quite a few people who don't own television sets, it's not that uncommon. The TV licensing people don't really believe that though, so you've still got to respond to those unpleasant "we think you're probably breaking the law" letters once a year.

## Comment: Re:Missing option (Score 1)171171

I wanted Role Playing Games too, so clicked the option "pen & pencil" as being the closest, although having the word "dice" in there would have helped.

## Comment: Re:Benefits, but still misses the point... (Score 1)698698

I'm 32, and in my whole life I've only seen a few guns in the UK. There were some air rifles in my school rifle club, and a couple of guns when I was in the ATC as a teenager. I don't know anyone who admits to owning a gun. I visited the US for 5 weeks when I was 15, and saw loads of them (I found it incredibly intimidating).

A very cursory check suggests that there are around 1.8 million guns in the UK, mostly in rural areas. That's 1 for every 35 people. So yes, there may be some guns, but the UK is a different situation to the US.

## Comment: Re:Benefits, but still misses the point... (Score 1)698698

At the risk of going against the general feeling, here in the UK we don't have any guns, and we have remarkably few school shootings. I honestly don't think that bringing more guns to the mix would make us safer. Yes, there are knife attacks, but it's considerably harder to kill people with a knife than with a gun, and running away is a realistic solution.

However the US has the problem that it already tolerates guns, so you need to find a different solution. Bringing more guns to the mix is going to make things safer. Stopping people having them in the first place would be a more sensible approach, but the 2nd amendment prevents that. This is not trolling or flamebait, but I personally find it very hard to justify that law: overthrowing a bad government would take more than just shooting a bunch of old men in the White House, you'd need to take on the military, and they have tanks, so you'll keep on having children dying as the years drag on for no appreciable benefit.

I really hope that the US can find a way to help troubled kids, to make it so they don't feel that the only option to get noticed is to kill the people around them, and the only solution at that point is to kill them before they kill to many others, but I don't think the system is set up that way.

## Comment: Re:Why..... (Score 1)259259

That would be awful. Your system would immediately hurt poor people, and benefit rich people, and since poor people vastly outnumber the rich, you'll end up harming the economy too, both through huge numbers of people buying less because they're worse off, and rich people paying less.

Taxing necessities the same as luxuries also hits poor people more, as they rely on the former. You need *progressive* taxation to account for people's ability to pay, since a flat tax for a poor person hurts much more than the same amount for a rich person.

Taxes are also there to penalise harmful activities. For example, there is a huge tax on tobacco that pays for treatment of cigarette smokers 5 times over (in the UK at least, I'm guessing you're from the US if you have hospital bills). Losing that would be a huge hit to medical care. Similarly, there are taxes on fuel and carbon usage to help prevent air pollution, since global warming is a huge problem that we face (okay, we'll ignore that state that decided to tax fuel efficient cars to make up for lost income, that was just stupid).

## California Governor Vetoes Bill Requiring Warrants For Drone Surveillance115115

schwit1 sends word that California governor Jerry Brown has vetoed legislation that would have required warrants for surveillance using unmanned drones. In his veto message (PDF), Brown said, "This bill prohibits law enforcement from using a drone without obtaining a search warrant, except in limited circumstances. There are undoubtedly circumstances where a warrant is appropriate. The bill's exceptions, however, appear to be too narrow and could impose requirements beyond what is required by either the 4th Amendment or the privacy provisions in the California Constitution."

The article notes that 10 other states already require a warrant for routine surveillance with a drone (Florida, Idaho, Illinois, Indiana, Iowa, Montana, Oregon, Tennessee, Utah, and Wisconsin). Further, Brown's claims about the bill's exceptions are overstated — according to Slate, "California's drone bill is not draconian. It includes exceptions for emergency situations, search-and-rescue efforts, traffic first responders, and inspection of wildfires. It allows other public agencies to use drones for other purposes — just not law enforcement."

## Comment: They were consumed by Cthulhu (Score 0)209209

No, really. I bought my younger sister (who was still living with our parents at the time) a plush Cthulhu for her birthday. 3 months later my parents called to let me know they'd had to throw out the entire toy basket, including my favourite Rocky the penguin, who my father brought back from his time in the Falkland's war, and who had travelled across Europe with me.

It turned out that clothes moths had got into the wicker basket where the toys were kept, and massacred the lot. With just one survivor... plush Cthulhu, who'd apparently remained untouched.

## Comment: Re:Probably a bad idea, but... (Score 1)192192

Sorry about your bizarre voting system. Just because I wanted better for my own country, doesn't mean I'd forgotten about the others out there.

Oh well, at least we get some democracy, even if it's not everything it could be.

## Comment: Re:Probably a bad idea, but... (Score 1)192192

That's not all correct. Scotland is definitely governed from Westminster, however there are certain issues (running of the NHS, education etc.) that are devolved to the Scottish parliament in Holyrood (since 1997). Westminster can revoke devolved powers, and can therefore overrule Holyrood. There have been many occasions when Scotland has been forced to comply with things it strongly disagreed with (e.g. recent foreign wars, the bedroom tax). Also, all tax raised in Scotland is sent to Westminster, and we are then given back an amount that includes money raised from borrowing. If Westminster decides to privatise the NHS, and decrease funding, then Scotland will also lose funding. If Westminster signs the TTIP, then it still affects the Scottish NHS, despite our control.

We do have an equal vote, however at 1/10th the population size, that means that as a country we get very little say in who governs us. We currently have a Conservative / Lib Dem coalition government, but only 1 single Conservative seat in Scotland. Basically, it doesn't matter how we vote, our government usually only reflects our wishes by coincidence. Whether or not this is fair (since this is general fact of life when groups aggregate, they get less control), is subjective.

Scotland has *always* had a different legal system to the one in England and Wales.

## Comment: Re:Shetland and Orkney (Score 1)192192

It is slightly closer to Scotland (but you're right, they do tend to *feel* closer to Norway). I've got relatives on Shetland, and they don't seem that bothered by it all.

That said, I voted Yes for independence today, and I have no problem with Shetland leaving to join Norway if that's what they want. I don't really see how they'll be able to lay claim to all (or any) of the oil though, that really is just Scotland's.

## Recipe For Building a Cheap Raspberry Pi Honeypot Network6868

mask.of.sanity (1228908) writes "Honeypots are the perfect bait for corporate IT shops to detect hackers targeting and already within their networks and now a guide has been published to build a dirt cheap battalion of the devices from Raspberry Pis. "By running honeypots on our internal network, we are able to detect anomalous events. We gain awareness and insight into our network when network hosts interact with a Raspberry Pi honeypot sensor," the author explained."

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