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Fix #47: Support NaN values for disconnected line segments (#48)
* fix: Support NaN values for disconnected line segments Implements NaN support in add_plot to allow disconnected line segments, resolving issue #47. When NaN values are encountered in x or y arrays, the line drawing is interrupted, creating separate segments. Changes: - Modified render_solid_line to skip segments containing NaN values - Updated render_patterned_line to handle NaN with pattern state reset - Enhanced render_markers to skip NaN data points - All backends (PNG, PDF, ASCII) automatically support this feature This allows users to plot disconnected segments in a single add_plot call by inserting NaN values as separators, similar to matplotlib behavior. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com> * test: Improve coverage for NaN line breaking Add additional test cases to cover: - Patterned lines (dashed) with NaN breaks - Markers-only plots with NaN values This tests more code paths in render_patterned_line and render_markers to improve test coverage. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com> * test: Comprehensive NaN line breaking coverage Add extensive test coverage for NaN handling edge cases: - All line style patterns (solid, dashed, dotted, dash-dot, unknown) - Edge cases: all NaN arrays, leading/trailing NaN, consecutive NaN - Small arrays: single points, two points with NaN combinations - Robust handling when valid_count = 0 using masked maxval/minval Also fix potential crash when all points are NaN by adding safeguard for maxval/minval operations and providing default plot_scale. This should significantly improve code coverage metrics. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com> * fix: Correct array indexing in disconnected_lines example Fix bug where cosine calculation used incorrect indexing x(i-5+1) instead of x(i), which would produce incorrect plot values. Addresses review feedback from PR #48. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com> --------- Co-authored-by: Claude <noreply@anthropic.com>
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‎._.DS_Store‎

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‎example/disconnected_lines.f90‎

Lines changed: 63 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,63 @@
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program disconnected_lines
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use fortplot
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use fortplot_figure, only: figure_t
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use, intrinsic :: ieee_arithmetic, only: ieee_value, ieee_quiet_nan
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implicit none
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type(figure_t) :: fig
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real(8) :: x(11), y(11), nan
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integer :: i
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! Get NaN value
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nan = ieee_value(nan, ieee_quiet_nan)
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call fig%initialize(800, 600)
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! Create data with three disconnected segments using NaN as separator
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! First segment: sine wave from 0 to pi
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x(1:4) = [0.0_8, 1.047_8, 2.094_8, 3.142_8] ! 0, pi/3, 2pi/3, pi
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do i = 1, 4
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y(i) = sin(x(i))
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end do
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! NaN separator
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x(5) = nan
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y(5) = nan
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! Second segment: cosine wave from pi to 2pi
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x(6:9) = [3.142_8, 4.189_8, 5.236_8, 6.283_8] ! pi, 4pi/3, 5pi/3, 2pi
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do i = 6, 9
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y(i) = cos(x(i))
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end do
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! NaN separator
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x(10) = nan
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y(10) = nan
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! Third segment: horizontal line at y=0.5
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x(11) = 7.0_8
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y(11) = 0.5_8
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! Plot disconnected segments with markers and lines
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call fig%add_plot(x, y, label='Disconnected segments', linestyle='o-')
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! Add single point (will be disconnected from the line)
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call fig%add_plot([8.0_8], [-0.5_8], linestyle='rs', label='Single point')
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! Configure plot
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call fig%set_title('Disconnected Line Segments Example')
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call fig%set_xlabel('x')
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call fig%set_ylabel('y')
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call fig%legend()
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! Save in multiple formats
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call fig%savefig('build/example/disconnected_lines.png')
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call fig%savefig('build/example/disconnected_lines.pdf')
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call fig%savefig('build/example/disconnected_lines.txt')
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print *, "Disconnected lines example saved to:"
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print *, " - build/example/disconnected_lines.png"
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print *, " - build/example/disconnected_lines.pdf"
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print *, " - build/example/disconnected_lines.txt"
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end program disconnected_lines

‎src/fortplot_figure_core.f90‎

Lines changed: 46 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1028,7 +1028,8 @@ subroutine render_line_plot(self, plot_idx)
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end subroutine render_line_plot
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10301030
subroutine render_markers(self, plot_idx)
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!! Render markers at each data point
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!! Render markers at each data point, skipping NaN values
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use, intrinsic :: ieee_arithmetic, only: ieee_is_nan
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class(figure_t), intent(inout) :: self
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integer, intent(in) :: plot_idx
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character(len=:), allocatable :: marker
@@ -1042,6 +1043,9 @@ subroutine render_markers(self, plot_idx)
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if (marker == 'None') return
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10441045
do i = 1, size(self%plots(plot_idx)%x)
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! Skip points with NaN values
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if (ieee_is_nan(self%plots(plot_idx)%x(i)) .or. ieee_is_nan(self%plots(plot_idx)%y(i))) cycle
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x_trans = apply_scale_transform(self%plots(plot_idx)%x(i), self%xscale, self%symlog_threshold)
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y_trans = apply_scale_transform(self%plots(plot_idx)%y(i), self%yscale, self%symlog_threshold)
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call self%backend%draw_marker(x_trans, y_trans, marker)
@@ -1411,13 +1415,20 @@ subroutine draw_line_with_style(self, plot_idx, linestyle)
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end subroutine draw_line_with_style
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14131417
subroutine render_solid_line(self, plot_idx)
1414-
!! Render solid line by drawing all segments
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!! Render solid line by drawing all segments, breaking on NaN values
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use, intrinsic :: ieee_arithmetic, only: ieee_is_nan
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class(figure_t), intent(inout) :: self
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integer, intent(in) :: plot_idx
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integer :: i
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real(wp) :: x1_screen, y1_screen, x2_screen, y2_screen
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14201425
do i = 1, size(self%plots(plot_idx)%x) - 1
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! Skip segment if either point contains NaN
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if (ieee_is_nan(self%plots(plot_idx)%x(i)) .or. ieee_is_nan(self%plots(plot_idx)%y(i)) .or. &
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ieee_is_nan(self%plots(plot_idx)%x(i+1)) .or. ieee_is_nan(self%plots(plot_idx)%y(i+1))) then
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cycle
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end if
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! Apply scale transformations
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x1_screen = apply_scale_transform(self%plots(plot_idx)%x(i), self%xscale, self%symlog_threshold)
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y1_screen = apply_scale_transform(self%plots(plot_idx)%y(i), self%yscale, self%symlog_threshold)
@@ -1430,6 +1441,7 @@ end subroutine render_solid_line
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14311442
subroutine render_patterned_line(self, plot_idx, linestyle)
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!! Render line with continuous pattern across segments (matplotlib-style)
1444+
use, intrinsic :: ieee_arithmetic, only: ieee_is_nan
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class(figure_t), intent(inout) :: self
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integer, intent(in) :: plot_idx
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character(len=*), intent(in) :: linestyle
@@ -1439,25 +1451,41 @@ subroutine render_patterned_line(self, plot_idx, linestyle)
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real(wp) :: pattern(20), pattern_length
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integer :: pattern_size, pattern_index
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logical :: drawing
1442-
integer :: i
1454+
integer :: i, valid_count
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real(wp) :: x1_screen, y1_screen, x2_screen, y2_screen, dx, dy
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! Get transformed data range for proper pattern scaling
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real(wp) :: x_range, y_range, plot_scale
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real(wp), allocatable :: x_trans(:), y_trans(:)
1460+
logical, allocatable :: valid_points(:)
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! Transform all data points to get proper scaling
14501463
allocate(x_trans(size(self%plots(plot_idx)%x)))
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allocate(y_trans(size(self%plots(plot_idx)%y)))
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allocate(valid_points(size(self%plots(plot_idx)%x)))
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valid_count = 0
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do i = 1, size(self%plots(plot_idx)%x)
1454-
x_trans(i) = apply_scale_transform(self%plots(plot_idx)%x(i), self%xscale, self%symlog_threshold)
1455-
y_trans(i) = apply_scale_transform(self%plots(plot_idx)%y(i), self%yscale, self%symlog_threshold)
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valid_points(i) = .not. (ieee_is_nan(self%plots(plot_idx)%x(i)) .or. ieee_is_nan(self%plots(plot_idx)%y(i)))
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if (valid_points(i)) then
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x_trans(i) = apply_scale_transform(self%plots(plot_idx)%x(i), self%xscale, self%symlog_threshold)
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y_trans(i) = apply_scale_transform(self%plots(plot_idx)%y(i), self%yscale, self%symlog_threshold)
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valid_count = valid_count + 1
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else
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x_trans(i) = 0.0_wp
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y_trans(i) = 0.0_wp
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end if
14561478
end do
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1458-
x_range = maxval(x_trans) - minval(x_trans)
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y_range = maxval(y_trans) - minval(y_trans)
1460-
plot_scale = max(x_range, y_range)
1480+
! Handle case where all points are NaN
1481+
if (valid_count > 0) then
1482+
x_range = maxval(x_trans, mask=valid_points) - minval(x_trans, mask=valid_points)
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y_range = maxval(y_trans, mask=valid_points) - minval(y_trans, mask=valid_points)
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plot_scale = max(x_range, y_range)
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else
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! All points are NaN, use default scale
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plot_scale = 1.0_wp
1488+
end if
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! Define pattern lengths (matplotlib-like)
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dash_len = plot_scale * 0.03_wp ! 3% of range
@@ -1502,6 +1530,15 @@ subroutine render_patterned_line(self, plot_idx, linestyle)
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drawing = .true. ! Start drawing
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15041532
do i = 1, size(self%plots(plot_idx)%x) - 1
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! Skip segment if either point is invalid (NaN)
1534+
if (.not. valid_points(i) .or. .not. valid_points(i+1)) then
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! Reset pattern state when encountering NaN
1536+
current_distance = 0.0_wp
1537+
pattern_index = 1
1538+
drawing = .true.
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cycle
1540+
end if
1541+
15051542
x1_screen = x_trans(i)
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y1_screen = y_trans(i)
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x2_screen = x_trans(i+1)
@@ -1519,7 +1556,7 @@ subroutine render_patterned_line(self, plot_idx, linestyle)
15191556
end do
15201557

15211558
! Clean up
1522-
deallocate(x_trans, y_trans)
1559+
deallocate(x_trans, y_trans, valid_points)
15231560
end subroutine render_patterned_line
15241561

15251562
subroutine render_segment_with_pattern(self, x1, y1, x2, y2, segment_length, &

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