Add histogram plot type

Author: jchristopherson

src/CMakeLists.txt

@@ -42,5 +42,6 @@ set(FPLOT_SOURCES
     ${dir}/fplot_plot_data_3d.f90
     ${dir}/fplot_surface_plot_data.f90
     ${dir}/fplot_stats_plots.f90
+    ${dir}/fplot_plot_histogram.f90
 )
 set(FPLOT_SOURCES ${FPLOT_SOURCES} PARENT_SCOPE)

src/fplot_plot_histogram.f90

@@ -0,0 +1,53 @@
+module fplot_plot_histogram
+    use iso_fortran_env
+    use fplot_plot_bar
+    use fplot_plot_data
+    use fplot_plot_data_histogram
+    use strings
+    implicit none
+    private
+
+    type, extends(plot_bar) :: plot_histogram
+        !! Defines a 2D plot tailored towards histogram plotting.
+    contains
+    end type
+contains
+! ------------------------------------------------------------------------------
+function ph_get_cmd(this) result(rst)
+    !! Gets the GNUPLOT commands required to draw the plot.
+    class(plot_histogram), intent(in) :: this
+        !! The plot_histogram object.
+    character(len = :), allocatable :: rst
+        !! The command string.
+
+    ! Local Variables
+    integer(int32) :: i, n
+    real(real64) :: minX, maxX
+    type(string_builder) :: str
+    class(plot_data), pointer :: pd
+
+    ! Cycle over the data and determine the min and max values from the data
+    n = this%get_count()
+    maxX = -huge(1.0d0)
+    minX = huge(1.0d0)
+    do i = 1, n
+        pd => this%get(i)
+        if (.not.associated(pd)) cycle
+        select type (pd)
+        class is (plot_data_histogram)
+            maxX = max(maxX, pd%get_maximum_value())
+            minX = min(minX, pd%get_minimum_value())
+        end select
+    end do
+
+    ! Define the x axis tic labels
+
+    ! Call the base method
+    call str%append(this%plot_bar%get_command_string())
+
+    ! End
+    rst = str%to_string()
+end function
+
+! ------------------------------------------------------------------------------
+end module