tasks a-s

Task/Polynomial-regression/Tcl/polynomial-regression.tcl

@@ -0,0 +1,49 @@
+package require math::linearalgebra
+
+proc build.matrix {xvec degree} {
+    set sums [llength $xvec]
+    for {set i 1} {$i <= 2*$degree} {incr i} {
+        set sum 0
+        foreach x $xvec {
+            set sum [expr {$sum + pow($x,$i)}]
+        }
+        lappend sums $sum
+    }
+
+    set order [expr {$degree + 1}]
+    set A [math::linearalgebra::mkMatrix $order $order 0]
+    for {set i 0} {$i <= $degree} {incr i} {
+        set A [math::linearalgebra::setrow A $i [lrange $sums $i $i+$degree]]
+    }
+    return $A
+}
+
+proc build.vector {xvec yvec degree} {
+    set sums [list]
+    for {set i 0} {$i <= $degree} {incr i} {
+        set sum 0
+        foreach x $xvec y $yvec {
+            set sum [expr {$sum + $y * pow($x,$i)}]
+        }
+        lappend sums $sum
+    }
+
+    set x [math::linearalgebra::mkVector [expr {$degree + 1}] 0]
+    for {set i 0} {$i <= $degree} {incr i} {
+        set x [math::linearalgebra::setelem x $i [lindex $sums $i]]
+    }
+    return $x
+}
+
+# Now, to solve the example from the top of this page
+set x {0   1   2   3   4   5   6   7   8   9  10}
+set y {1   6  17  34  57  86 121 162 209 262 321}
+
+# build the system A.x=b
+set degree 2
+set A [build.matrix $x $degree]
+set b [build.vector $x $y $degree]
+# solve it
+set coeffs [math::linearalgebra::solveGauss $A $b]
+# show results
+puts $coeffs