ex-7: keep negative sign in perceptron weights

ex-7/percep.c

@@ -85,8 +85,6 @@ gsl_vector *percep_train(
    * comparison with other methods.
    */
   double norm = gsl_blas_dnrm2(w);
-  if (gsl_vector_isneg(w))
-    norm = -norm;
   gsl_vector_scale(w, 1/norm);
   *cut = -bias/norm;
 

ex-7/plot.py

@@ -25,7 +25,7 @@ scatter(*signal, edgecolor='xkcd:charcoal',
 scatter(*noise,  edgecolor='xkcd:charcoal',
         c='xkcd:pale purple', label='noise')
 line(-20*w, 20*w, c='xkcd:midnight blue', label='projection')
-line(w-10*v, w+10*v, c='xkcd:scarlet', label='cut')
+line(abs(w)-10*v, abs(w)+10*v, c='xkcd:scarlet', label='cut')
 xlabel('x')
 ylabel('y')
 xlim(-1.5, 8)