[icyspirit]

Summary

Arithmetic of signals. A signal can be computed from other signals and from numbers:

• the operators +, -, * and /, with the usual precedence and parentheses;
• deriv(x): d/dt for time traces, d/dx for profiles (in the order of x);
• abs(x), and norm(x), which now also takes an expression.

equilibrium/time_slice/global_quantities/ip - summary/global_quantities/ip/value
core_profiles/profiles_1d/t_i_average / core_profiles/profiles_1d/electrons/temperature
core_profiles/profiles_1d/electrons/temperature / core_profiles/profiles_1d/electrons/temperature[0]
deriv(summary/global_quantities/ip/value) * 1e-6
abs(pf_active/coil[:]/current/data)

• Division: / also separates the nodes of a path, so a division has spaces around it (a / b). A / right after a path, with no space, belongs to the path. Plain paths parse as before, including norm(), transpose(), Fortran indices, [-1] and odd spacing.
• Alignment: two signals are combined on the times and the grid of the first.
  • For traces, the second is interpolated in time, and is NaN outside its range. A single sample counts only at its own time.
  • For profiles and maps, the second is taken at its closest time slice within its time range and interpolated onto the grid of the first. Maps use a separable bilinear interpolation.
  • A time trace applies to profiles and maps at their times, e.g. a profile divided by its central value.
  • A static profile or map combined with a time trace becomes time-dependent.
  • Profiles against different coordinates are an error.
• Wildcards: signals combine member by member, by the names both have, or in order when all members are renamed; or each member is combined with the same signal.
• Labels and units: the result is labeled with the expression. The units follow:
  • those of a sum or difference;
  • none for a ratio of like quantities;
  • a/b and a.b for other quotients and products;
  • per second for deriv of a trace.
• Evaluation: a data source evaluates an expression from its cached signals and caches the result.
  • Missing data in any operand is still a gray note, not an error.
  • Alternatives (a - b | c) can be expressions.

Sources relative to the first. A panel can show every source but the first relative to the first, signal by signal:

• relative: difference shows B − A, and relative: ratio shows B / A, using the same arithmetic.
• It is set in three places: the configuration, a sources choice in the setup dialog, and a Sources submenu in the panel's context menu (undoable).
• The first source is then not drawn, and the legend says what is compared ([B − A]). The y and colorbar titles say Δ … or … ratio.
• The scale of a signal still applies to a difference. The offset cancels out, so it does not apply, and a ratio has neither.
• Shapes cannot be compared: a map of B − A keeps each source's boundary, and the line-style legend then names those sources (A, B).
• A single source is shown as it is.
• The crosshair of the Point mode reads what is drawn, so it gives B − A or B / A.

Docs: the README (signal paths, panel comparison, configuration keys), the path tooltip in the setup dialog, and the module documentation.

Notes

• The expression layer (idscope.data.expressions) sits on top of SignalPath:
  • parse_alternatives returns SignalPaths for plain paths, as before, and Expressions otherwise.
  • An Expression stands wherever a path does (text, label, name, canonical()).
  • DataSource.signal evaluates it.
• Parsing tries the expression grammar first. If that fails, it falls back to the old path parser, so paths written with spaces inside still work. When both fail, the more relevant error is reported: the expression's when the text looks like an expression, e.g. "unknown function 'sqrt' (available: …)".
• transpose() must still take a path: it reorders dimensions before the data is extracted.
• No new dependency: interpolation uses numpy only.
• Main merged in (the crosshair of feat: a crosshair with the values under the mouse in Point mode #14 and the device template of feat: a device template, with vessel layers and conductors as shapes #15). The conflicts were only side by side: imports, the panel's attributes, and tests appended at the same place.

Test plan

• QT_QPA_PLATFORM=offscreen pytest: 228 passed in the dev environment, a clean PySide6 6.11 environment and a PyQt5 5.15 environment, after merging main. The clean installs were rebuilt without a stale build/ directory.
• New tests:
  • parsing:
    • plain paths stay paths, including norm(), transpose(), Fortran indices and spaces;
    • precedence and parentheses in the labels;
    • a/b vs a / b;
    • [-1] is not a subtraction;
    • canonical forms;
    • alternatives;
    • errors: trailing operator, unbalanced brackets, unknown function, transpose of an expression, **, a bare IDS name, a number alone;
  • on the demo: traces, units, deriv, abs, the cache, profiles (ratio, over the central value, deriv, norm of an expression, different coordinates), maps, members, shapes refused, and what a source does not have (note, and fallback to the next alternative);
  • arithmetic, on synthetic data: interpolation and time ranges, constants and single samples, profiles on grids and closest slices, a static profile times a trace, maps on another grid and at the times of a trace, members by name, renamed or disjoint, derivatives with repeated or NaN times and decreasing x, relative_to;
  • configuration: round trip and invalid value;
  • GUI:
    • expressions in a panel, with the red error for an unknown function;
    • difference, ratio and map difference, each with its names, values, scale and offset, legend and colorbar title;
    • the crosshair on a difference (Ip (equilibrium) [B − A] = -0.2);
    • the Sources menu, and undo;
    • a single source shown as it is;
    • the setup dialog choice.
• Screenshot checked: B − A, B / A, the equilibrium Ip minus the summary Ip, dIp/dt, Te/Te(0), and a psi map difference with both boundaries.
• pyflakes src tests reports nothing.

🤖 Generated with Claude Code

https://claude.ai/code/session_018aVekYzCRLPE71Mm6UH8Zp

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Generated by Claude Code