Add gnuplot annotation hook and LaTeX-like arrow/equation 3-line example

watsonryan · watsonryan · commit d97af3a7fa99 · 2026-02-25T14:44:56.000Z
diff --git a/examples/three_line_ieee_example.cpp b/examples/three_line_ieee_example.cpp
@@ -35,6 +35,9 @@ int main(int argc, char** argv) {
   ax.legend = true;
   ax.grid = true;
   ax.ylog = true;
+  ax.gnuplot_commands = {
+      "set label 1 'e_p(t)=e_0 e^{-{/Symbol l} t}' at 18,4.0 font 'Times,8'",
+      "set arrow 1 from 34,3.6 to 58,1.9 lw 1.0 lc rgb '#000000'"};
   fig.axes(0).set(ax);
 
   std::vector<double> t;
diff --git a/include/gnuplotpp/plot.hpp b/include/gnuplotpp/plot.hpp
@@ -70,6 +70,9 @@ struct AxesSpec {
 
   bool xlog = false;
   bool ylog = false;
+
+  // Optional raw gnuplot commands for advanced annotations (arrows/labels/etc).
+  std::vector<std::string> gnuplot_commands;
 };
 
 /** @brief Supported series drawing types. */
diff --git a/src/gnuplot_backend.cpp b/src/gnuplot_backend.cpp
@@ -231,6 +231,10 @@ void emit_plot_body(std::ostream& os,
       os << "set yrange [" << axis_spec.ymin << ":" << axis_spec.ymax << "]\n";
     }
 
+    for (const auto& cmd : axis_spec.gnuplot_commands) {
+      os << cmd << "\n";
+    }
+
     if (axis.series().empty()) {
       os << "plot 1/0 notitle\n";
       continue;
