XRT DEM Iterative Solver Module

[joyvelasquez]

Summary

This PR introduces XRTDEMIterative, a Python implementation of the IDL
routine xrt_dem_iterative2.pro for estimating Differential Emission
Measures (DEMs) from Hinode/XRT multi-filter observations.

What's Included

Core Solver (dem_solver.py)

• XRTDEMIterative class with full DEM solving pipeline
• Spline-parameterized DEM representation with iterative least-squares
  fitting via lmfit
• Temperature response interpolation onto a regular log10(T) grid
• User-supplied or default intensity uncertainty model:
  max(0.03 * intensity, 2 DN/s/pix), matching IDL default behavior
• Monte Carlo uncertainty estimation via monte_carlo_runs parameter
• Input validation with informative warnings (saturation, negative
  intensities, missing errors)
• summary() method for diagnostic output

Plotting (dem_plotting.py)

• plot_dem() — base DEM solution visualization
• plot_dem_mc() — base DEM + Monte Carlo ensemble overlay

Tests

• 70+ unit tests covering input validation, grid construction,
  response interpolation, spline system, residuals, solver, and
  Monte Carlo behavior
• Currently - heavy work in progress (UPDATED JULY 2026)

Documentation

• dem_overview.rst — introduction to DEM analysis with XRTpy
• API reference for xrtpy.xrt_dem_iterative
• Changelog entry in docs/changelog/0.6.0.rst

Validation -

• Validated against IDL xrt_dem_iterative2.pro across multiple
  solar observation cases using Monte Carlo comparison
• Currently - heavy work in progress (UPDATED JULY 2026)

[joyvelasquez]

Ensure the function checks for minimum required inputs (filters, observed intensities, etc.) and validates that all observation values are non-zero before proceeding.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2560 lines in your changes missing coverage. Please review.
✅ Project coverage is 36.28%. Comparing base (28a2e02) to head (bb258ef).

Files with missing lines	Patch %	Lines
xrtpy/xrt_dem_iterative/test/test_dem_solver.py	0.00%	502 Missing ⚠️
xrtpy/xrt_dem_iterative/dem_solver.py	0.00%	386 Missing ⚠️
...rative/test/older_testing_methods/plots_results.py	0.00%	294 Missing ⚠️
...ive/test/older_testing_methods/idl_vs_xrtpy_dem.py	0.00%	265 Missing ⚠️
xrtpy/xrt_dem_iterative/test/plot_mc_comparison.py	0.00%	211 Missing ⚠️
...t_dem_iterative/test/test_dem_idl_comparison_mc.py	0.00%	168 Missing ⚠️
xrtpy/xrt_dem_iterative/test/utils_sav_io.py	0.00%	164 Missing ⚠️
...py/xrt_dem_iterative/test/plot_idl_vs_xrtpy_dem.py	0.00%	149 Missing ⚠️
...rative/test/older_testing_methods/utils_case_io.py	0.00%	117 Missing ⚠️
.../xrt_dem_iterative/test/test_dem_idl_comparison.py	0.00%	114 Missing ⚠️
... and 4 more

❗ There is a different number of reports uploaded between BASE (28a2e02) and HEAD (bb258ef). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (28a2e02)	HEAD (bb258ef)
	2	1

Additional details and impacted files

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- Coverage   87.35%   36.28%   -51.07%     
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  Files          26       40       +14     
  Lines        1819     4379     +2560     
  Branches      106      334      +228     
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  Hits         1589     1589               
- Misses        184     2744     +2560     
  Partials       46       46               

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[namurphy]

Thinking about compatibility with GenericModel in sunkit-dem, it would help to add attributes for temperature_bin_centers and temperature_bin_widths to XRTDEMIterative.