added images_contours_and_fields/contourf_log.cpp, and ticker

gallery/images_contours_and_fields/CMakeLists.txt

 add_demo(quiver_demo quiver_demo.cpp)
+add_demo(contourf_log contourf_log)
 
 add_custom_target(images_contours_and_fields
-  DEPENDS quiver_demo
+  DEPENDS quiver_demo contourf_log
   COMMAND quiver_demo
-  COMMENT "running quiver_demo"
+  COMMAND contourf_log
+  COMMENT "running images_contours_and_fields"
   WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../images"
 )

gallery/images_contours_and_fields/contourf_log.cpp

+// example from
+// https://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_log.html
+
+#include <matplotlibcpp17/pyplot.h>
+#include <matplotlibcpp17/cm.h>
+#include <matplotlibcpp17/ticker.h>
+
+#include <xtensor/xbuilder.hpp>
+#include <xtensor/xview.hpp>
+#include <xtensor/xmath.hpp>
+
+#include <vector>
+
+using namespace std;
+using namespace matplotlibcpp17;
+using namespace xt::placeholders;
+
+using mesh2D = vector<vector<double>>;
+
+int main() {
+  const int N = 100;
+  auto x_ = xt::linspace(-3.0, 3.0, N);
+  auto y_ = xt::linspace(-2.0, 2.0, N);
+
+  auto [X_, Y_] = xt::meshgrid(x_, y_);
+  auto Z1_ = xt::exp(-xt::pow(X_, 2) - xt::pow(Y_, 2));
+  auto Z2_ = xt::exp(-xt::pow(X_ * 10, 2) - xt::pow(Y_ * 10, 2));
+  xt::xarray<double> z_ = Z1_ + 50 * Z2_;
+  // instead of x[:5, :5] = -1.0
+  auto v = xt::view(z_, xt::range(_, 5), xt::range(_, 5));
+  v = 0.0;
+  // to vector<vector>>
+  const int xsz = x_.shape()[0], ysz = y_.shape()[0];
+  mesh2D X(xsz), Y(xsz), z(xsz);
+  for (int i = 0; i < xsz; ++i) {
+    X[i].resize(ysz);
+    Y[i].resize(ysz);
+    z[i].resize(ysz);
+    for (int j = 0; j < ysz; ++j) {
+      X[i][j] = X_(i, j);
+      Y[i][j] = Y_(i, j);
+      z[i][j] = z_(i, j);
+    }
+  }
+
+  py::scoped_interpreter guard{};
+  // to numpy array
+  auto Xpy = py::array(py::cast(std::move(X)));
+  auto Ypy = py::array(py::cast(std::move(Y)));
+  auto zpy = py::array(py::cast(std::move(z)));
+  auto plt = pyplot::import();
+  auto [fig, ax] = plt.subplots();
+  auto cs = ax.contourf(Args(Xpy, Ypy, zpy),
+                        Kwargs("locator"_a = ticker::LogLocator().unwrap(),
+                               "cmap"_a = cm::PuBu_r()));
+  fig.colorbar(Args(cs));
+  plt.show();
+}

include/matplotlibcpp17/axes.h

@@ -69,6 +69,10 @@ public:
   pybind11::object contour(const pybind11::tuple &args = pybind11::tuple(),
                            const pybind11::dict &kwargs = pybind11::dict());
 
+  // contourf
+  pybind11::object contourf(const pybind11::tuple &args = pybind11::tuple(),
+                            const pybind11::dict &kwargs = pybind11::dict());
+
   // errorbar
   pybind11::object errorbar(const pybind11::tuple &args = pybind11::tuple(),
                             const pybind11::dict &kwargs = pybind11::dict());
@@ -226,6 +230,7 @@ private:
 #endif
     LOAD_FUNC_ATTR(barh, self);
     LOAD_FUNC_ATTR(contour, self);
+    LOAD_FUNC_ATTR(contourf, self);
     LOAD_FUNC_ATTR(errorbar, self);
     LOAD_FUNC_ATTR(fill, self);
     LOAD_FUNC_ATTR(fill_between, self);
@@ -276,6 +281,7 @@ private:
   pybind11::object bar_label_attr;
   pybind11::object barh_attr;
   pybind11::object contour_attr;
+  pybind11::object contourf_attr;
   pybind11::object errorbar_attr;
   pybind11::object fill_attr;
   pybind11::object fill_between_attr;
@@ -375,6 +381,13 @@ pybind11::object Axes::contour(const pybind11::tuple &args,
   return obj;
 }
 
+// contourf
+pybind11::object Axes::contourf(const pybind11::tuple &args,
+                                const pybind11::dict &kwargs) {
+  pybind11::object obj = contourf_attr(*args, **kwargs);
+  return obj;
+}
+
 // errorbar
 pybind11::object Axes::errorbar(const pybind11::tuple &args,
                                 const pybind11::dict &kwargs) {

include/matplotlibcpp17/cm.h

@@ -16,6 +16,12 @@ pybind11::object coolwarm() {
   return ret;
 }
 
+pybind11::object PuBu_r() {
+  pybind11::object ret =
+      pybind11::module::import("matplotlib.cm").attr("PuBu_r");
+  return ret;
+}
+
 } // namespace matplotlibcpp17::cm
 
 #endif /* MATPLOTLIBCPP17_CM_H */

include/matplotlibcpp17/ticker.h

+/**
+ * @file ticker.h
+ * @brief corresponding header for matplotlib.ticker
+ **/
+
+#ifndef MATPLOTLIBCPP17_TICKER_H
+#define MATPLOTLIBCPP17_TICKER_H
+
+#include <pybind11/pybind11.h>
+
+#include <matplotlibcpp17/common.h>
+
+namespace matplotlibcpp17::ticker {
+
+struct DECL_STRUCT_ATTR LogLocator : public BaseWrapper {
+public:
+  LogLocator() {
+    pybind11::object attr =
+        pybind11::module::import("matplotlib.ticker").attr("LogLocator");
+    self = attr();
+  }
+};
+
+} // namespace matplotlibcpp17::ticker
+
+#endif /* MATPLOTLIBCPP17_ANIMATION_H */