Add spline interpolation

Author: jchristopherson

examples/CMakeLists.txt

@@ -77,3 +77,9 @@ add_executable(distribution_example distribution_example.f90)
 target_link_libraries(distribution_example fstats)
 target_link_libraries(distribution_example ${fplot_LIBRARY})
 target_include_directories(distribution_example PUBLIC ${fplot_INCLUDE_DIR})
+
+# Interpolation Example
+add_executable(interpolation_example interpolation_example.f90)
+target_link_libraries(interpolation_example fstats)
+target_link_libraries(interpolation_example ${fplot_LIBRARY})
+target_include_directories(interpolation_example PUBLIC ${fplot_INCLUDE_DIR})

examples/interpolation_example.f90

@@ -0,0 +1,65 @@
+program example
+    use iso_fortran_env
+    use fstats
+    use fplot_core
+    implicit none
+
+    ! Parameters
+    integer(int32), parameter :: n = 9
+    integer(int32), parameter :: m = 100
+
+    ! Local Variables
+    type(spline_interpolator) :: interp
+    real(real64) :: x(n), y(n), xi(m), yi1(m), yi2(m)
+
+    ! Plot Variables
+    type(plot_2d) :: plt
+    type(plot_data_2d) :: pd1, pd2, pd3
+    class(legend), pointer :: lgnd
+
+    ! Initialization
+    x = [-4.0d0, -3.0d0, -2.0d0, -1.0d0, 0.0d0, 1.0d0, 2.0d0, 3.0d0, 4.0d0]
+    y = [0.0d0, 0.15d0, 1.12d0, 2.36d0, 2.36d0, 1.46d0, 0.49d0, 0.06d0, &
+        0.0d0]
+    xi = linspace(minval(x), maxval(x), m)
+
+    ! Interpolation - Default
+    call interp%initialize(x, y)
+    call interp%interpolate(xi, yi1)
+
+    ! Interpolation - defined slope at both ends
+    call interp%initialize(x, y, &
+        ibcbeg = SPLINE_KNOWN_FIRST_DERIVATIVE, ybcbeg = 0.0d0, &
+        ibcend = SPLINE_KNOWN_FIRST_DERIVATIVE, ybcend = 0.0d0)
+    call interp%interpolate(xi, yi2)
+
+    ! Plot the results
+    call plt%initialize()
+    lgnd => plt%get_legend()
+    call lgnd%set_is_visible(.true.)
+
+    call pd1%define_data(x, y)
+    call pd1%set_name("Data")
+    call pd1%set_draw_line(.false.)
+    call pd1%set_draw_markers(.true.)
+    call pd1%set_marker_style(MARKER_X)
+    call pd1%set_marker_scaling(2.0)
+    call pd1%set_line_width(2.0)
+    call pd1%set_line_color(CLR_BLACK)
+    call plt%push(pd1)
+
+    call pd2%define_data(xi, yi1)
+    call pd2%set_name("Default")
+    call pd2%set_line_width(2.0)
+    call pd2%set_line_color(CLR_RED)
+    call plt%push(pd2)
+
+    call pd3%define_data(xi, yi2)
+    call pd3%set_name("Enforced End Slope")
+    call pd3%set_line_style(LINE_DASHED)
+    call pd3%set_line_width(2.0)
+    call pd3%set_line_color(CLR_BLUE)
+    call plt%push(pd3)
+
+    call plt%draw()
+end program

src/fstats.f90

@@ -132,4 +132,9 @@ module fstats
     public :: base_interpolator
     public :: linear_interpolator
     public :: polynomial_interpolator
+    public :: spline_interpolator
+    public :: SPLINE_QUADRATIC_OVER_INTERVAL
+    public :: SPLINE_KNOWN_FIRST_DERIVATIVE
+    public :: SPLINE_KNOWN_SECOND_DERIVATIVE
+    public :: SPLINE_CONTINUOUS_THIRD_DERIVATIVE
 end module