1 #include "Stats.h" 2 3 //----------------------------------------------------------------------------- 4 5 double chooseK ( int n, int k ) 6 { 7 if(k > (n - k)) k = n - k; 8 9 double c = 1; 10 11 for(int i = 0; i < k; i++) 12 { 13 double t = double(n-i) / double(i+1); 14 15 c *= t; 16 } 17 18 return c; 19 } 20 21 double chooseUpToK ( int n, int k ) 22 { 23 double c = 0; 24 25 for(int i = 1; i <= k; i++) 26 { 27 c += chooseK(n,i); 28 } 29 30 return c; 31 } 32 33 //----------------------------------------------------------------------------- 34 // Distribution "score" 35 // TODO - big writeup of what this score means 36 37 // Basically, we're computing a constant that says "The test distribution is as 38 // uniform, RMS-wise, as a random distribution restricted to (1-X)*100 percent of 39 // the bins. This makes for a nice uniform way to rate a distribution that isn't 40 // dependent on the number of bins or the number of keys 41 42 // (as long as # keys > # bins * 3 or so, otherwise random fluctuations show up 43 // as distribution weaknesses) 44 45 double calcScore ( const int * bins, const int bincount, const int keycount ) 46 { 47 double n = bincount; 48 double k = keycount; 49 50 // compute rms value 51 52 double r = 0; 53 54 for(int i = 0; i < bincount; i++) 55 { 56 double b = bins[i]; 57 58 r += b*b; 59 } 60 61 r = sqrt(r / n); 62 63 // compute fill factor 64 65 double f = (k*k - 1) / (n*r*r - k); 66 67 // rescale to (0,1) with 0 = good, 1 = bad 68 69 return 1 - (f / n); 70 } 71 72 73 //---------------------------------------------------------------------------- 74 75 void plot ( double n ) 76 { 77 double n2 = n * 1; 78 79 if(n2 < 0) n2 = 0; 80 81 n2 *= 100; 82 83 if(n2 > 64) n2 = 64; 84 85 int n3 = (int)n2; 86 87 if(n3 == 0) 88 printf("."); 89 else 90 { 91 char x = '0' + char(n3); 92 93 if(x > '9') x = 'X'; 94 95 printf("%c",x); 96 } 97 } 98 99 //----------------------------------------------------------------------------- 100
