How do I calculate the normal vector of a line segment? [closed]
If we define dx = x2 – x1 and dy = y2 – y1, then the normals are (-dy, dx) and (dy, -dx). Note that no division is required, and so you’re not risking dividing by zero.
math
Why use softmax as opposed to standard normalization?
There is one nice attribute of Softmax as compared with standard normalisation. It react to low stimulation (think blurry image) of your neural net with rather uniform distribution and to high stimulation (ie. large numbers, think crisp image) with probabilities close to 0 and 1. While standard normalisation does not care as long as the … Read more
How can I specify the base for Math.log() in JavaScript?
“Change of Base” Formula / Identity The numerical value for logarithm to the base 10 can be calculated with the following identity. Since Math.log(x) in JavaScript returns the natural logarithm of x (same as ln(x)), for base 10 you can divide by Math.log(10) (same as ln(10)): function log10(val) { return Math.log(val) / Math.LN10; } Math.LN10 … Read more
Circle line-segment collision detection algorithm?
Taking E is the starting point of the ray, L is the end point of the ray, C is the center of sphere you’re testing against r is the radius of that sphere Compute: d = L – E ( Direction vector of ray, from start to end ) f = E – C ( … Read more
Why prefer two’s complement over sign-and-magnitude for signed numbers?
It’s done so that addition doesn’t need to have any special logic for dealing with negative numbers. Check out the article on Wikipedia. Say you have two numbers, 2 and -1. In your “intuitive” way of representing numbers, they would be 0010 and 1001, respectively (I’m sticking to 4 bits for size). In the two’s … Read more
Remove insignificant trailing zeros from a number?
I had a similar instance where I wanted to use .toFixed() where necessary, but I didn’t want the padding when it wasn’t. So I ended up using parseFloat in conjunction with toFixed. toFixed without padding parseFloat(n.toFixed(4)); Another option that does almost the same thing This answer may help your decision Number(n.toFixed(4)); toFixed will round/pad the … Read more
Mod of negative number is melting my brain
I always use my own mod function, defined as int mod(int x, int m) { return (x%m + m)%m; } Of course, if you’re bothered about having two calls to the modulus operation, you could write it as int mod(int x, int m) { int r = x%m; return r<0 ? r+m : r; } … Read more
Why does Python’s hash of infinity have the digits of π?
Summary: It’s not a coincidence; _PyHASH_INF is hardcoded as 314159 in the default CPython implementation of Python, and was picked as an arbitrary value (obviously from the digits of π) by Tim Peters in 2000. The value of hash(float(‘inf’)) is one of the system-dependent parameters of the built-in hash function for numeric types, and is … Read more
Rounding BigDecimal to *always* have two decimal places
value = value.setScale(2, RoundingMode.CEILING)
How do I calculate a point on a circle’s circumference?
The parametric equation for a circle is x = cx + r * cos(a) y = cy + r * sin(a) Where r is the radius, cx,cy the origin, and a the angle. That’s pretty easy to adapt into any language with basic trig functions. Note that most languages will use radians for the angle … Read more