p3(lrls): redo how explicit works

p3/lrls/arx.go

@@ -30,7 +30,7 @@ func Estimate(eMethod int, u, y []float64) ([][]float64, []float64, error) {
 
 	switch method {
 	case methodExplicit:
-		theta, errs, err = explicit()
+		err = explicit()
 
 	case methodRecursive:
 		theta, errs, err = recursive(u, y)

p3/lrls/explicit.go

@@ -5,15 +5,15 @@ import (
 	"os/exec"
 )
 
-func explicit() ([][]float64, []float64, error) {
+func explicit() error {
 	err := runExplicitMatlab()
 	if err != nil {
-		return nil, nil, err
+		return err
 	}
 
 	// TODO: read data processed and saved by matlab and return that.
 
-	return nil, nil, nil
+	return nil
 }
 
 func runExplicitMatlab() error {