Ask MetaFilter questions tagged with maths

Masters in maths? Difficulty level: Have bachelors in graphic design

Cat Set Go — Sun, 31 Mar 2013 11:08:49 -0800

Dear Mefites, a long time ago I got a degree in graphic design but never worked in the industry. Along the way I somehow (don't remember how or why or when) became interested in math and I finished a graduate diploma in maths as a distance learning course in my free time. I am considering applying for masters programmes in maths or related subjects but ... can I? Should I? To give a little more background, I'm interested in what I perceive as stuff related to applied maths: meteorology, language processing, cryptography, etcetera. But I'm also wondering how I can relate these sorts of interests to jobs or careers ...

I've seen center for women in mathematics and LEAP but I'm not a US citizen and I can't afford to attend those. Also, I have no access to education I'm interested in where I live, hence I'm considering becoming an international student in the EU. I have some savings but by no means can I afford to get a second bachelors degree ...

I've also tried looking for work in related fields so I could get a feel for them but right now I'm just stuck at an awful data entryish job that I hate so much.

And also sometimes I feel like I'm so stupid that I just shouldn't be attempting this at all ... argh!

I'd appreciate any advice! Thank you!

Weighted mean

djgh — Mon, 31 Dec 2012 10:07:48 -0800

Mathematics-filter: If there are seven funds with various charges, how can I work out the allocation to these funds of a fixed amount so that the weighted mean charge is below a certain level and the allocations are of similar sizes? Background: I'm looking at putting some of my savings in index trackers. In order to try and balance risk, I would like to spread my savings around various tracker funds, which have varying levels of charges. I would like to keep charges below a certain level, and try and keep the investment in each fund roughly similar (otherwise the risk isn't so evenly spread).

The seven funds have the following charges:
Fund 1: 0.57%
Fund 2: 0.57%
Fund 3: 0.59%
Fund 4: 0.62%
Fund 5: 0.62%
Fund 6: 0.65%
Fund 7: 0.71%

My (admittedly extremely limited) maths skills are failing me - the closest I could get was the allocation of savings (i.e. weighting) for each charge rate, but then this leaves those funds with the same rate receiving half of the relevant allocation, which means that the amount in each fund is not balanced.

How can I work out what percentage of my savings should be placed in each fund so that the average charge is 0.58% or lower, whilst the amount in each fund is as similar as possible?

Human Random Generator

Foci for Analysis — Fri, 21 Dec 2012 16:47:33 -0800

Can you think of a method that allows an individual to pseudo randomly create a sequence of numbers (at the very least the randomness is opaque to the minds of other people) assuming said individual may only use his mind and body (no physical tools are allowed)? Some use cases to test this method:
* tell someone a number between 1-100
* select 10 out out of 20 doors and select 5 out of those 10
* create a string consisting of 10 ascii characters
* select a date and time (YYYY-MM-DD, HH:MM)

Sherlock as a Mathematical Logician?

Anon Ymous — Wed, 12 Dec 2012 19:01:43 -0800

A colleague alluded to a passage from Sherlock Holmes where all the evidence is re-written as formal logic propositions, leading to a mathematical solution that matches Holmes' solution (and is far from trivial). Does anyone else know where I could find this passage? I'm a maths teacher and will be teaching Logic to top level year 11s in the new year, and this sounded interesting. Unfortunately, my google-fu is only turning up introductions to logic with quotes from Sherlock Holmes, rather than the full passage with formal logic notation beside it - I would *really* appreciate any help.

Thanks :)

What should my sample size be?

xchmp — Mon, 12 Nov 2012 08:36:03 -0800

Say that I have a bag which contains 100 balls and every ball in the bag should be red, but it's possible that one or more of these balls is the wrong colour. How many balls should I look at to be 90% sure that all the balls are red? Or 95%? Or 99.9%? Talk me through how to work this out, please?

Percentage Calculation

jontyjago — Fri, 19 Oct 2012 16:15:51 -0800

I know the price of something now and what the price was 2 years ago - how do I calculate that as an annual percentage increase? I live in Argentina where inflation is (unofficially) estimated at 25% annually. I remember that 2 years ago a kilo of ice cream at my local shop was 29 kilos. It's now 48 pesos. That's a 71% increase over 2 years - how do I calculate that on an annual basis (assuming the same increase each year)?

I've worked it out using trial and error, but I'm looking for a formula I can use and apply to other figures.

What part of the earth gets the most moonlight?

zinful — Sat, 06 Oct 2012 15:49:35 -0800

Is there any place on Earth that gets the most moonlight? Hey astronomers! I don't know if this even makes sense to ask, but my partner and I have been kicking around whether there is any place on Earth that gets what could be described as the most moonlight. Moonlight only counts as times where it is only the moon showing, not also the sun (since it's reflected light from the sun, I know this seems arbitrary, but I'm not looking for just visible moon, since the light really does look different).

Is there any way to determine this?
Does the whole Earth get the same amount of moonlight per year?
How would one even start to figure this out (astronomy was many years ago)?

How do I calculate the probability of a specific sum of repeated die rolls?

Richard Daly — Fri, 28 Sep 2012 22:16:58 -0800

I'm looking to learn how to calculate probabilities for a multi-round dice game. I've researched this question some, and it looks like I might need to know how to use the multinomial distribution, but I can't find any good introductions. Please point me to the most layman-accessible educational material on this subject, and help me to help myself. The game I'm playing can be abbreviated like this:

I roll two six sided dice and add them.
I then subtract a (fixed) penalty value, and score as many points as remain.
I cannot score less than 0. If I would score less than 0 points, I score 0 instead.
I repeat this process several times, without altering the penalty between rolls.

How do I predict the probability of any 1 particular cumulative score?
I am not interested in simulating this event and taking a random sample; I want to calculate all possible outcomes and their precise probabilities. Examples follow:

Example #1:
My penalty value is 0, and I repeat the die roll 36 times.
Each roll will produce a number between 2 and 12 inclusive, and my final score will be between 72 and 432. What is the chance that I will score 7 points exactly 6 times.

Example #2:
My penalty value is 11, and I repeat the procedure 40 times.
Each roll will produce a value between 0 and 1 inclusive, and my final total score will be between 0 and 40, and likely closer to 0 than 40.
I wish to predict the chance that I will score a cumulative total of exactly 2 points across the sum of all 40 trials.

Example #3:
My penalty value is -5, and I repeat the procedure 5 times.
Each roll will produce a value between 7 and 17 inclusive (negative penalty). I wish to plot the probability of a arriving at each possible total: 35 through 85.

Again, I think maybe this is a case of the muiltinomial distribution, but everything I can find about it (wikipedia) is confusing and not written as educational but as reference material.

I'm familiar with MS Excel and have a basic Liberal Arts understanding of calculus and probability/statistics, though I'm quite rusty. I'm willing to re-learn what I have forgotten, and also to learn new skills - within reason. If this procedure requires me to learn lots of new math, I would appreciate links or book titles to pursue as well as a general outline of what the fields of study are called, and what I'll need to know to pursue them intelligently (i.e. help me ask questions without sounding ignorant/clueless).

I gather that the program R might be helpful in this, so please feel free to recommend a good introduction to both R and Statistics.

Thanks for any help you're able to give!

Getting my math(s) right.

cincinnatus c — Tue, 10 Jul 2012 08:53:13 -0800

Maths (math) people of the US: I need your help in working out if certain British conventions would be understood or standard in the US classroom. I'm working on some text that will be read by schoolkids in the US. There is a fair bit of math involved, and while I'm confident I've "translated" most of it properly there are a few things I'm not sure about:

1. "The formula that describes the steps can be applied to find any triangular number, where T(n) is the sum of the numbers from one to n"

Is T(n) correct in the US here?

2. "Firstly, Newton developed differential calculus, a method for calculating the gradient of a curve on a graph."

Should "gradient" be "slope" here?

3. Vectors/coordinates. I have the sentence "To calculate the vector that describes the movement of an object between two points, like an aeroplane, the coordinates at point A are subtracted from point B" illustrated with something like:

B(2, 10, 4) - A(5,0,5) = AB (-3,10,-1)

except that there the numbers in the parantheses are piled on top of each other rather than being separated by commas, as in the numerous examples in this link
AND
there is a right-facing arrow above "AB"

Is this how this should be presented in the US?

4. "The gradient of a straight line is calculated by dividing the change in vertical height by the change in horizontal distance. At first, the flat ocean bed has a zero gradient – there is no slope at all. Despite moving only a few millimeters each year, folds develop over time, and a slight gradient of 0.1, or 10%, builds up. Over millions of years the fold mountain continues to grow and, as the gradient gets steeper, it rises above sea level. "

Again, should all of these "gradient"s be "slope"s? Or should they be "grade"s, because we're talking about mountains? Or a mix of the two?

Thanks for your help!

Taking the random out of racking

omnigut — Wed, 04 Apr 2012 16:24:22 -0800

After tens of thousands of games of pool, every time I rack the balls I seem to switch about half of them around. I know I'm wasting time. So, I want to know exactly how many balls I should normally expect to swap (the median), and what is the most I should ever have to swap. For those of you who aren't pool nerds like me, I've explained the 8-ball racking process inside. A "proper" rack should look something like this.

There are 15 balls. 7 "stripes", 7 "solids", and one black ball.

You dump them into the triangle at random, then swap them around until you have the "correct" pattern. There are two different recognised patterns (European and American), but we'll pretend there's just one.

You can either start that pattern with stripes at the front, or solids. You can also reverse the pattern in terms of symmetry. As such, I think there are four ways of racking the balls correctly.

However, once the balls are in, you can spin the triangle into three positions, giving you 12 total possibilities.

There is a complication: the black is the only ball that has to sit on one of the inside three spots.

So, if the balls happen to land in the worst possible way, what are the most number of ball swaps that you'll ever have to make? I'm talking about straight swaps — no moving three at a time.

A second, perhaps more-important question: what's the median starting position, in terms of how many ball swaps I'll have to make?

What is the difference between floating point accuracy and precision?

conrad101 — Mon, 02 Jan 2012 14:54:45 -0800

What is the difference between floating point accuracy and precision?

Maths for tiny people?

nj554 — Sat, 13 Aug 2011 08:32:05 -0800

How to teach math to a 3.5 year old? Posting for a friend:

A friend of mine has asked me to give maths lessons to his 3.5 year old son, and I'd like to help - but I don't know where to start.

What sort of "math" is it reasonable to try to teach to someone so young? And what would be the best way of teaching it? Are there maths games I could use?

Thanks in advance!

If an geeky child is traveling South at 839 MPH, and his nerdy dad is going North at...

bondcliff — Wed, 08 Jun 2011 10:43:33 -0800

My son, who is finishing up third grade, loves math and especially the basic Algebra he's been doing. He is actually sad to be leaving school for the summer because he's so into it. How can I keep this going for him over the summer? Fun books, board games, computer (on-line and OSX) games? Seriously, Jason Fox is this kid's idol. He desperately wants to learn Calculus, though I don't think he even knows what that is. For now he's happy doing algebra such as "2x + 5 = -7 + 10x" (Those are just random letters and numbers. I have not checked if that's a legit equation. I spent my summers avoiding math, you see)

He's finishing up 3rd grade at a Montessori school, ready to go into forth, or "Upper El" as they call it. While I want him to have the usual summer of playing Minecraft, chucking rocks at beehives, and frolicking merrily outside I'd like to keep him entertained with whatever math he's willing to do.

So what can I give him? While computer games are fun I would prefer non-computer things if they exist. Interesting books (not just books of random problems), board games, TV-shows, YouTube videos, activities, etc. I'm happy to know about any computer games as well. We're Mac people, at least at home. Really anything that will engage him and help him to understand the math he's doing.

He is a nine year old, and while he's advanced in math for his age he is still a kid, so anything should be somewhat age appropriate.

Everything I give him will be optional for him over the summer, of course. I'm not interested in pushing him where he doesn't want to go.

Did Anyone Invent Some New Math Stuff So They Could Solve A Problem Which Then Lead To a Technological Breakthrough?

Brian Puccio — Wed, 06 Apr 2011 13:16:19 -0800

Can you cite any examples where a technological breakthrough wasn't possible until there was some sort of mathematical breakthrough? I've been told that Egyptians were able to forge ahead in geometry, which better allowed them to figure out the areas of their fields. I'm not exactly sure how useful this is, but this is the best example I can think of.

I'm also somewhat familiar with Leibniz and Newton and calculus, but did either of them start with a problem to solve, "figure out" integral calculus and then use it to solve their problem?

Did anyone else make a breakthrough once they figured out new mathematical techniques?

Mathematics help for 6yr old son

sammyabdu — Tue, 05 Apr 2011 17:55:19 -0800

Help me help my 6yr old with maths. My son is in Year 1 (First grade) and is struggling with addition & subtraction, which are the basics.
I'm not sure how to help him as I'm embarrassingly bad at explaining things.
His father and I help him daily with his homework but I think all we're doing is confusing him with our own methods and he's already generally not very sure of himself unfortunately.
I'm just looking for a simple and fun way to teach him. What effective method will stick? Counters, base ten or just using his fingers to count? Any suggestions will be appreciated.

Is not the headbutt somewhat pyrrhic?

dougrayrankin — Thu, 24 Feb 2011 16:32:23 -0800

Help me understand the efficacy of a headbutt as an offensive opening gambit in a bout of fisticuffs... I've been thinking it over, and it seems to me to be a problem of the conservation of momentum. That is to say, m1v1 = m2v2. From a purely mathematical standpoint I imagine that one would do as much harm to oneself as to one's opponent (all heads being of equal mass). Am I missing some key element? Please, I find myself a rather confused man.

Help me figure out the algorithm to solve a maths problem

WizKid — Mon, 14 Feb 2011 07:01:55 -0800

Need help from Math and IT geeks :-) Long question inside. I'm trying to implement a program to compute the following.

inputs to the program values P, U and L. Then I create a 3D matrix PxPx(U-L+1)
For the sake of clarity lets assume P=2, U=1, L=-1
I need all the different combinations of 4 items alone Z axis.
In this instance the different combinations are as follows. (In each iteration I feed these 4 values to another function for calculations. Here for simplicity I potrait it as just addition)
matrix is as follows coeff[x][y][z]

t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][1]

//-------------
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][1]
//-------------
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][-1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][1]
//======================
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][1]

//-------------
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][1]
//-------------
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][0] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][1]
//========================
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][-1] + coeff[1][0][1] + coeff[1][1][1]

//-------------
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][0] + coeff[1][0][1] + coeff[1][1][1]
//-------------
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][-1] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][0] + coeff[1][1][1]

t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][-1]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][0]
t = coeff[0][0][1] + coeff[0][1][1] + coeff[1][0][1] + coeff[1][1][1]

I'm trying to do this in C++, but only need help in figuring out the algorithm. So even if your answer is not in C++ that's fine.

for (int k1=-1;k1<=1;k1++){
for (int k2=-1;k2<=1;k2++){
for (int k3=-1;k3<=1;k3++){
for (int k4=-1;k4<=1;k4++){
cout << "x[0][0]["<<k1<<"] \t";
cout << "x[0][1]["<<k2<<"] \t";
cout << "x[1][0]["<<k3<<"] \t";
cout << "x[1][1]["<<k4<<"]\n";
}
}
}
}

Above is a piece of code (mefi messed up my indentations) I wrote assuming all the values are constants. SO most of the things are hard coded. But my program needs to accept P, U and L as inputs and create the output on the fly.

Picking the correct probability distribution

alby — Thu, 13 Jan 2011 01:28:10 -0800

Which probability distribution should I use to model examination results? At the moment I'm using the Beta distribution, but that's mainly because it looks right and is relatively easy to implement in Excel, which is what I use as a markbook. I don't think that the normal distribution is correct because that'd create a symmetric graph and the results are usually biased around one end of the scale, but I wonder about other distributions.

I'm a scientist, so I can understand the maths, but I haven't done a lot of stats work and so I don't know which distribution is appropriate for which situation.

system dynamics

moorooka — Tue, 21 Dec 2010 17:47:42 -0800

Maths-filter: please recommend some good resources (books, sites, software) for learning about numerical simulations of large (like 20+ dimensional) dynamical systems, especially in continuous time. I have pretty basic Matlab and R skills, but that's about it... wondering if learning Mathematica would be worth the effort, or even something like C.

Answering to Sir What is x

92_elements — Thu, 11 Nov 2010 11:16:25 -0800

But Sir, what is x? Teaching students algebra for the first time. They keep wanting to put values in for x, and write that down. E.g. x + x = . Becomes 1 + 1 = 2, in their books. Whereas I want x + x = 2x. Does anyone have any strategies, or techniques to overcome this? My understanding of algebra came years later around 16-17, due to properly understanding Sets. Unfortunately, the students don't have any sort of Set knowledge, neither do I have the time to teach it them.

Thank you.

Mean means and modish modes

mippy — Wed, 20 Oct 2010 08:16:42 -0800

Statistics! I need to use them at work, but over the past few years numbers seem to make my head spin. Any tips for parsing them? Any recommended books for someone who only scraped a C at GCSE Maths? I often need to look at data - averages, percentages, sales figures, that kind of thing - to assess claims for my job. I think I've just stopped feeling confident with numbers - I struggle to add, my brain shuts down when I play boardgames that involve a lot of maths (Race for the Galaxy being a good example - the very similar San Juan is easy to me) and I even get nervous when I do crafts that involve counting rows or stitches. I have no idea why this is - I've struggled with a few cognitive tasks since a period of illness a few years ago - but I do worry when it affects my work.

I open a spreadsheet and it's like my brain flashes up a 'DOES NOT COMPUTE' message. Sometimes this is because the figures I need to see are necessarily complicated, but often I feel I should be able to comprehend this information as easily as text but just can't.

I have wondered about taking GCSE Statistics but this course doesn't seem to be available to adults who work full-time. I didn't enjoy maths at school which I think made competency all the harder, but I'm at the point now where my skills are becoming a sticking point. Accuracy is vital for my job so I want to improve and help myself as much as possible. Any advice?

I NEED MATHS! How do I slow this track down to -800%?

tunestunes — Mon, 13 Sep 2010 20:07:51 -0800

How do I reduce something by -800% when I'm working with a scale between -99% and 99%? I saw this and i wanted to see if I'd get roughly the same result with similar songs. I tried slowing down John Mayer's "Waiting on the World to Change" in Audacity but it will only allow me to slow something down by 99 or -99% at a time. If only I had taken math class more seriously could I figure this out! So I how do I get this John Mayer track down to the -800% it deserves to be heard at? Thanks!

"Latex Pictures"

moorooka — Tue, 07 Sep 2010 17:06:36 -0800

Help! I need (in a hurry) to put my matlab images into a latex document. I'm exporting them as eps files, but when I put them in the latex file, all the text (legends and axis labels) have vanished. I can't find a solution on google. I can't use jpg instead because it looks crap. Why is the text in my eps file not showing up??

SDEs

moorooka — Sun, 29 Aug 2010 02:18:51 -0800

Where can I find a proof for the strong order of convergence of the Euler-Maruyama or Milstein schemes used to model stochastic differential equations?

Learning curve?

zingzangzung — Thu, 26 Aug 2010 18:45:25 -0800

Can someone help me with a maths problem please, how to find y for a given x on a curve? I am struggling with some probably basic maths. I understand so little maths that I don't know the right terms to use but I'll try and explain.
This image shows a curve. I am trying to find the equation which will let me find y for a given x on a curve like this.
http://imgur.com/hxCWk.png

I want to be able to try different scales on x and y axes and get the resulting numbers for y. I have no idea how to do this. And it's not homework, I am a long time out of school.