added quiver example

Author: matthew-hennefarth

examples/vector_fields/quiver/CMakeLists.txt

@@ -14,4 +14,6 @@ add_executable(example_quiver_5 quiver_5.cpp)
 target_link_libraries(example_quiver_5 PUBLIC matplot)
 
 
+add_executable(example_quiver_6 quiver_6.cpp)
+target_link_libraries(example_quiver_6 PUBLIC matplot)
 

examples/vector_fields/quiver/quiver_6.cpp

@@ -0,0 +1,19 @@
+#include <cmath>
+#include <matplot/matplot.h>
+
+int main() {
+    using namespace matplot;
+    auto [x, y] = meshgrid(iota(-2.5, 0.25, 2.5), iota(-2.5, 0.25, 2.5));
+    vector_2d u =
+        transform(x, y, [](double x, double y) { return cos(x)*sin(x + y); });
+    vector_2d v =
+        transform(x, y, [](double x, double y) { return sin(y)*cos(x + y); });
+
+    vector_2d m =
+        transform(u, v, [](double u, double v) { return sqrt(u * u + v * v); });
+
+    quiver(x, y, u, v, m, 0.2)->normalize(true).line_width(1.5);
+
+    show();
+    return 0;
+}