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gaussian_rand() -> gaussian_rands(), log_rand() -> log_rands()

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Revar Desmera
2019-11-06 22:19:19 -08:00
parent 5addbe8184
commit 5cca83958f
4 changed files with 63 additions and 20 deletions
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math.scad
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@@ -259,39 +259,49 @@ function log2(x) = ln(x)/ln(2);
// min = Minimum integer value to return.
// max = Maximum integer value to return.
// N = Number of random integers to return.
// seed = Random number seed.
// seed = If given, sets the random number seed.
// Example:
// ints = rand_int(0,100,3);
// int = rand_int(-10,10,1)[0];
function rand_int(min,max,N,seed=undef) =
function rand_int(min, max, N, seed=undef) =
assert(max >= min, "Max value cannot be smaller than min")
let (rvect = is_def(seed) ? rands(min,max+1,N,seed) : rands(min,max+1,N))
[for(entry = rvect) floor(entry)];
// Function: gaussian_rand()
// Function: gaussian_rands()
// Usage:
// gaussian_rand(mean, stddev)
// gaussian_rands(mean, stddev, [N], [seed])
// Description:
// Returns a random number with a gaussian/normal distribution.
// Arguments:
// mean = The average random number returned.
// stddev = The standard deviation of the numbers to be returned.
function gaussian_rand(mean, stddev) =
let(s=rands(0,1,2)) mean + stddev*sqrt(-2*ln(s.x))*cos(360*s.y);
// N = Number of random numbers to return. Default: 1
// seed = If given, sets the random number seed.
function gaussian_rands(mean, stddev, N=1, seed=undef) =
let(nums = is_undef(seed)? rands(0,1,N*2) : rands(0,1,N*2,seed))
[for (i = list_range(N)) mean + stddev*sqrt(-2*ln(nums[i*2]))*cos(360*nums[i*2+1])];
// Function: log_rand()
// Function: log_rands()
// Usage:
// log_rand(minval, maxval, factor);
// log_rands(minval, maxval, factor, [N], [seed]);
// Description:
// Returns a single random number, with a logarithmic distribution.
// Arguments:
// minval = Minimum value to return.
// maxval = Maximum value to return. `minval` <= X < `maxval`.
// factor = Log factor to use. Values of X are returned `factor` times more often than X+1.
function log_rand(minval, maxval, factor) =
-ln(1-rands(1-1/pow(factor,minval), 1-1/pow(factor,maxval), 1)[0])/ln(factor);
// N = Number of random numbers to return. Default: 1
// seed = If given, sets the random number seed.
function log_rands(minval, maxval, factor, N=1, seed=undef) =
assert(maxval >= minval, "maxval cannot be smaller than minval")
let(
minv = 1-1/pow(factor,minval),
maxv = 1-1/pow(factor,maxval),
nums = is_undef(seed)? rands(minv, maxv, N) : rands(minv, maxv, N, seed)
) [for (num=nums) -ln(1-num)/ln(factor)];
// Function: segs()