output 0-1 matrix by default

cmd/internal/graph/dot/graph.go

@@ -38,7 +38,14 @@ func NewDOTDirectedGraph(weightAttr string) *DOTDirectedGraph {
 
 // NewLine returns a DOT-aware weighted line.
 func (g *DOTDirectedGraph) NewLine(from, to graph.Node) graph.Line {
-	e := g.DirectedGraph.NewWeightedLine(from, to, math.NaN()).(multi.WeightedLine)
+	var defaultWeight float64
+	if g.WeightAttribute == "" {
+		defaultWeight = 1
+	} else {
+		defaultWeight = math.NaN()
+	}
+
+	e := g.DirectedGraph.NewWeightedLine(from, to, defaultWeight).(multi.WeightedLine)
 	return &weightedLine{WeightedLine: e, weightAttribute: g.WeightAttribute}
 }
 

cmd/internal/graph/dot/nodes_edges.go

@@ -17,7 +17,6 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package dot
 
 import (
-	"errors"
 	"strconv"
 
 	"gonum.org/v1/gonum/graph"
@@ -57,8 +56,6 @@ func (e *weightedLine) SetAttribute(attr encoding.Attribute) error {
 	switch attr.Key {
 	case e.weightAttribute:
 		e.W, err = strconv.ParseFloat(attr.Value, 64)
-	default:
-		err = errors.New("unknown key:" + attr.Key)
 	}
 
 	return err

cmd/root.go

@@ -150,7 +150,7 @@ func init() {
 
 	rootCmd.Flags().BoolVar(&oneline, "oneline", false, "output on one line")
 
-	rootCmd.Flags().StringVar(&weightAttr, "weight-attr", "len", "edge attribute to use as weight")
+	rootCmd.Flags().StringVar(&weightAttr, "weight-attr", "", "edge attribute to use as weight")
 
 	rootCmd.Flags().StringSliceVarP(&nodeOrder, "order", "o", nil, "order of nodes in rows/columns of output")
 }