ERPimage

[arnodelorme]

• color scheme (turbo)
• alignments of plots
• missing scalp topo on top

[claude]

🤖 Plan:

• Read AGENTS.md, fix-issue and pull-request skills
• Fetch issue 300 and review the reference screenshot
• Locate ERP-image source and tests
• Duplicate-work preflight: no open PR touches erpimage
• Research + Proposed Fix (below)
• Branch agent/20260810-fix-300, add failing tests, implement fix
• ./pre-commit.py --fix + uv run pytest tests/test_phase4_plot_wrappers.py (82 passed, 4 MATLAB-only skipped)
• PR [EEG] pop_erpimage: turbo cmap, aligned ERP plot, scalp inset #302 open; CI green on all 3 Python versions × 3 OSes plus docs

Research

erpimage() uses cmap="RdBu_r", hangs the colorbar off image_ax with shrink=0.85, and labels the ERP y-axis "ERP". pop_erpimage never forwards channel identity, so no scalp topo is drawn even though the dialog exposes a plotmap checkbox. Measured axis positions confirm the layout drift: image_ax width = 0.673, erp_ax width = 0.841 (the ERP plot extends past the image column because tight_layout re-widens it once the colorbar is anchored to image_ax).

Relevant code

• src/eegprep/functions/sigprocfunc/erpimage.py#L41-L71 — figure/gridspec, RdBu_r, "ERP" y-label, shrink=0.85 colorbar.
• src/eegprep/functions/popfunc/pop_erpimage.py#L79-L93 — forwards options to erpimage(); no chan_locs/index passed.
• src/eegprep/functions/popfunc/pop_erpimage.py#L167-L168 — plotmap checkbox in dialog spec, currently ignored at runtime.
• src/eegprep/functions/sigprocfunc/topoplot.py#L326-L360 — _blank_topoplot(style='blank', axes=…) renders head/nose/ears without color, reusable for the scalp inset.

Proposed Fix

Rework the erpimage() figure to a gridspec with a dedicated colorbar column (width_ratios [20, 1]) so the image and ERP axes share the same left/right edges, switch the image cmap to "turbo", change the ERP y-label to "µV", and add an optional scalp-topo row on top rendered by topoplot([], chan_locs, style='blank', electrodes='off', axes=topo_ax) with a single marker at the plotted channel. pop_erpimage passes chan_locs=EEG['chanlocs'] and channel_index=index when typeplot=1 and plotmap is on (matching the existing dialog default). Components keep the existing 2-row layout — EEGLAB shows ICA scalp maps only with projchan, outside the scope of this issue.

Shipped in PR #302.