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Tag Archives: q
Generate all permutations in q/KDB+
My solution : perm:{[s] $[(count s)=1;s;[p:(rotate[1]\)s;raze((string first each p),/:’perm each 1_/:p)]]} Results : perm “a” “a” perm “ab” “ab” “ba” perm “abc” “abc” “acb” “bca” “bac” “cab” “cba” The kdb+ personal developers blog contains a thread on generating all the … Continue reading
Exponential Smoothing in q/KDB+
The formula for exponential smoothing is : S(1) = Y(0) S(t) = Alpha * Y(t) + (1-Alpha) S(t-1) 1) The corresponding solution in Q is : es:{{(x*z)+(1-x)*y}[x]\[y]} where, x is the smoothing factor(Alpha) and y is the list containing the … Continue reading
Greatest Common Divisor in Q/KDB+
Euclid’s algorithm : Recursive definition of the gcd function using Euclid’s algorithm is : function gcd(a, b) { if (b = 0) return a else return gcd(b, a mod b) } Solution in Q : g:{$[y=0;:x;:g[y;x mod y]];} Results : … Continue reading
Subvector grade down – Q Idioms 15
x:1 0 0 1 0 0 1 0 y:14 12 18 15 13 16 11 17 K solution : {,/x+’>:’x _ y}[&x;y] 2 0 1 5 3 4 7 6 Solution Posted : {raze x +’ idesc each x _ … Continue reading
Subvector grade up – QIdiom 7
x:1 0 0 1 0 0 1 0 y:14 12 18 16 13 15 11 17 Solution in K : {,/x+'<:’x _ y}[&x;y] 1 0 2 4 3 5 6 7 Solution Posted : {raze x +’ iasc each x … Continue reading
My experiments while learning q KDB + 