Data update

Task/Identity-matrix/DuckDB/identity-matrix.duckdb

@@ -0,0 +1,20 @@
+# Produce an (i,j,value) table representing the matrix I(m,n)
+# which is the identity matrix if m = n
+create or replace function I(m,n,zero) as table (
+   with recursive cte(i,j,ij,value) as (
+     select 1, 1, (null,null), zero
+     union all
+     select if(j=n, i+1,  i) as i,
+            if(j=n, 1,  j+1) as j,
+            (i, j) as ij,
+            zero + if(i=j, 1, 0) as value
+     from cte
+     where i <= m
+     )
+   select ij[1] as i, ij[2] as j, value
+   from cte
+   offset 1
+);
+
+# Generate a 3x3 matrix with DOUBLE(3,2) values:
+from I(3, 3, 0.000);