deal with rounding error in 2D y limits

pub/lib/plot.cpp

@@ -562,7 +562,7 @@ namespace {
         if (plot->Y.logflag && !(std::isfinite(yinf) && std::isfinite(ysup)))
             throw "No nonzero y values";
         if (!plot->Y.finite())
-            plot->Y.set_limits(yinf, ysup);
+            plot->Y.set_limits(yinf-1e-4*std::abs(yinf), ysup+1e-4*std::abs(ysup));
         // plot
         plot->start_frame2D("Frida version " VERSION);
         for (size_t j=0; j<m; ++j) {