Data update

Task/Cumulative-standard-deviation/DuckDB/cumulative-standard-deviation.duckdb

@@ -0,0 +1,7 @@
+# Create a table with the data together with a sequence number
+CREATE OR REPLACE TABLE t AS
+  SELECT generate_subscripts(l, 1) as id, unnest(l)::DOUBLE as x,
+  from (values ([2,4,4,4,5,5,7,9])) tbl(l) ;
+
+# Compute the rolling standard deviations without the Bessel adjustment:
+SELECT *, stddev_pop(x) OVER (ORDER BY id)  as 'cumulative stddev' FROM t;

Task/Cumulative-standard-deviation/Zig/cumulative-standard-deviation.zig

@@ -0,0 +1,21 @@
+const std = @import("std");
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+    const arr = [_]f32{ 2, 4, 4, 4, 5, 5, 7, 9 };
+
+    var sum: f32 = 0;
+    var sum2: f32 = 0;
+    var count: f32 = 0;
+
+    for (arr) |n| {
+        sum += n;
+        sum2 += std.math.pow(f32, n, 2);
+        count += 1;
+
+        const cumulative: f32 = count * sum2 - std.math.pow(f32, sum, 2);
+        const running_sd: f32 = std.math.sqrt(cumulative) / count;
+
+        try stdout.print("{d} {d}\n", .{n, running_sd});
+    }
+}