polylines to also take single arg

lib/PDL/Graphics/Simple.pm

@@ -768,7 +768,7 @@ $plot_options->synonyms( {
 });
 our $plot_types = {
   points    => { args=>[1,2], ndims=>[1]   },
-  polylines => { args=>[2],   ndims=>[1,2] },
+  polylines => { args=>[1,2], ndims=>[1,2] },
   lines     => { args=>[1,2], ndims=>[1]   },
   bins      => { args=>[1,2], ndims=>[1]   },
   circles   => { args=>[2,3], ndims=>[1]   },
@@ -970,6 +970,10 @@ sub _translate_plot {
     if ($ptn eq 'contours' and @args == 1) {
       my $cntr_cnt = 9;
       push @args, zeroes($cntr_cnt)->xlinvals($args[-1]->minmax);
+    } elsif ($ptn eq 'polylines' and @args == 1) {
+      barf "Single-arg form of '$ptn' must have dim 0 of 3"
+        if $args[0]->dim(0) != 3;
+      @args = ($args[0]->slice('0:1'), $args[0]->slice('(2)'));
     } elsif (defined($pt->{args}[1])) { # Add an index variable if needed
       barf "First arg to '$ptn' must have at least $pt->{ndims}[0] dims"
         if $args[0]->ndims < $pt->{ndims}[0];

t/simple.t

@@ -58,8 +58,10 @@ for my $bounds (5, {}, [1..3], [1,1]) {
 { my @w; local $SIG{__WARN__} = sub {push @w, @_};
 eval { PDL::Graphics::Simple::_translate_plot(undef, undef, with=>'lines', pdl(1), pdl(1), pdl(1)) };
 like $@, qr/requires 1 or 2 columns/;
+eval { PDL::Graphics::Simple::_translate_plot(undef, undef, with=>'fits', pdl(1), pdl(1)) };
+like $@, qr/requires 1 columns/;
 eval { PDL::Graphics::Simple::_translate_plot(undef, undef, with=>'polylines', pdl(1)) };
-like $@, qr/requires 2 columns/;
+like $@, qr/Single-arg/;
 is "@w", "", "no warnings";
 }