Add marginals_plot

docs/index.md

@@ -29,7 +29,6 @@
   </br></br>
 </div>
 
-
 ## Getting started
 
 ::::{grid} 2
@@ -120,6 +119,12 @@
 
 :::
 
+:::{grid-item-card} Marginals plot
+:link: plotting/marginals.ipynb
+:img-bottom: _static/plotting/marginals-plot.png
+
+:::
+
 ::::
 
 ## Custom figures

docs/plotting/index.md

@@ -58,6 +58,12 @@
 
 :::
 
+:::{grid-item-card} Marginals plot
+:link: marginals.ipynb
+:img-bottom: ../_static/plotting/marginals-plot.png
+
+:::
+
 ::::
 
 ```{toctree}
@@ -73,4 +79,5 @@ super-plot
 scatter-plot
 scatter3d-plot
 mesh3d-plot
+marginals
 ```

docs/plotting/marginals.ipynb

@@ -0,0 +1,106 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "0",
+   "metadata": {},
+   "source": [
+    "# Marginals plot\n",
+    "\n",
+    "The marginals plot shows a 2-dimensional image together with the 1-dimensional lines obtained from summing over each dimension."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import plopp as pp"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2",
+   "metadata": {},
+   "source": [
+    "## Basic marginals plot\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "da = pp.data.data2d()\n",
+    "pp.marginals(da)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "4",
+   "metadata": {},
+   "source": [
+    "## Control the side of the vertical plot\n",
+    "\n",
+    "Above, the 1D plot as a function of `y` is placed on the left and its data axis increases from right to left.\n",
+    "We can alternatively show it on the right. This also results in the axis increasing from left to right as is the more common case:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "5",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "pp.marginals(da, side=\"right\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "6",
+   "metadata": {},
+   "source": [
+    "## Extra arguments\n",
+    "\n",
+    "`marginals` supports some additional arguments like `title`. It also forward any extra arguments to the underlying plot functions, in this example, `grid`. Note that the arguments are passed to *all* three subplots."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "pp.marginals(da, title=\"My plot\", grid=True)"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.6"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

src/plopp/__init__.py

@@ -28,6 +28,7 @@
         'plotting': [
             'DimensionSlicer',
             'inspector',
+            'marginals',
             'mesh3d',
             'plot',
             'scatter',

src/plopp/plotting/__init__.pyi

@@ -2,6 +2,7 @@
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
 
 from ._inspector import inspector
+from ._marginals import marginals
 from ._mesh3d import mesh3d
 from ._plot import plot
 from ._scatter import scatter
@@ -13,6 +14,7 @@ from ._xyplot import xyplot
 __all__ = [
     'DimensionSlicer',
     'inspector',
+    'marginals',
     'mesh3d',
     'plot',
     'scatter',

src/plopp/plotting/_marginals.py

@@ -0,0 +1,128 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2026 Scipp contributors (https://github.com/scipp)
+
+from functools import partial
+from typing import Any, Literal
+
+import matplotlib.pyplot as plt
+import scipp as sc
+from mpl_toolkits.axes_grid1 import make_axes_locatable
+
+from ..backends.matplotlib.utils import make_figure
+from ..core import Node
+from ..core.typing import FigureLike
+from ..graphics import imagefigure, linefigure
+from .common import input_to_nodes, preprocess
+
+
+def marginals(
+    data: sc.DataArray | Node,
+    *,
+    side: Literal["left", "right"] = "left",
+    title: str = "",
+    cbar: bool = True,
+    ax: plt.Axes | None = None,
+    ignore_size: bool = False,
+    ignore_sorted: bool = False,
+    coords=None,
+    **plot_kwargs: Any,
+) -> FigureLike:
+    """Plot 2D data and the sums over each dim as a 1D plot.
+
+    This function plots ``data`` as a 2D image with a colorbar.
+    It also sums over each of its dimensions and plots the resulting 1D data
+    next to and above the main image.
+
+    .. versionadded:: 26.11.0
+
+    Parameters
+    ----------
+    data:
+        The data to plot. Must be 2-dimensional.
+    side:
+        Which side to show the 1D plot along the y-axis.
+        Note that when ``side == "left"``, the x-axis of the side plot is inverted,
+        i.e., it increases from right to left.
+    title:
+        Title of the plot.
+    cbar:
+        Whether to use a colorbar.
+    ax:
+        Optional axes to plot into. If None, ``marginals_plot`` creates new Axes.
+    ignore_size:
+            If ``True``, skip the check that prevents the rendering of very large data.
+    ignore_sorted:
+        Do not check if the coordinates are sorted before plotting.
+    coords:
+        If supplied, use these coords instead of the input's dimension coordinates.
+    **plot_kwargs:
+        Forwarded to *all* subplots :func:`plopp.graphics.linefigure`,
+        and :func:`plopp.graphics.imagefigure`.
+
+    Returns
+    -------
+    :
+        A figure that contains all axes.
+    """
+    if ax is None:
+        ax_2d = make_figure().subplots()
+    else:
+        ax_2d = ax
+
+    divider = make_axes_locatable(ax_2d)
+    ax_top = divider.append_axes("top", 1.2, pad=0.1, sharex=ax_2d)
+    ax_side = divider.append_axes(side, 1.2, pad=0.1, sharey=ax_2d)
+    cax = divider.append_axes("right", "4%", pad="5%") if cbar else None
+
+    main_data_node = input_to_nodes(
+        data,
+        processor=partial(
+            preprocess,
+            ignore_size=ignore_size,
+            ignore_sorted=ignore_sorted,
+            coords=coords,
+        ),
+    )
+
+    if len(main_data_node) > 1:
+        raise ValueError("The marginals plot accepts only a single data input.")
+    main_data_node = main_data_node[0]
+
+    fig = imagefigure(main_data_node, ax=ax_2d, cax=cax, cbar=cbar, **plot_kwargs)
+
+    # Main plot (2D)
+    y_label = ax_2d.get_ylabel()
+    if side == "left":
+        ax_2d.yaxis.set_tick_params(labelleft=False)
+        ax_2d.set_ylabel("")
+
+    # Top Plot
+    top_node = Node(lambda da: da.sum(da.dims[0]), main_data_node)
+    linefigure(top_node, ax=ax_top, title=title, **plot_kwargs)
+    ax_top.xaxis.set_tick_params(labelbottom=False)
+    ax_top.set_xlabel("")
+
+    # Side plot
+    def make_side_data(da: sc.DataArray) -> sc.DataArray:
+        if da.coords.is_edges(da.dims[0]):
+            raise sc.DimensionError(
+                "marginals() does not support bin edges along the y-axis."
+            )
+        summed = da.sum(da.dims[1])
+        return sc.DataArray(
+            data=summed.coords[summed.dim],
+            # rename to work around https://github.com/scipp/plopp/issues/616.
+            coords={summed.dim: summed.data},
+        ).rename({summed.dim: " "})
+
+    side_node = Node(make_side_data, main_data_node)
+    linefigure(side_node, ax=ax_side, **plot_kwargs)
+    ax_side.set_xlabel(ax_top.get_ylabel())
+    if side == "left":
+        ax_side.set_ylabel(y_label)
+        ax_side.invert_xaxis()
+    else:
+        ax_side.yaxis.set_tick_params(labelleft=False)
+        ax_side.set_ylabel("")
+
+    return fig

src/plopp/plotting/_plot.py

@@ -31,6 +31,7 @@ def plot(
     figsize: tuple[float, float] | None = None,
     grid: bool = False,
     ignore_size: bool = False,
+    ignore_sorted: bool = False,
     legend: bool | tuple[float, float] = True,
     hide_log_buttons: bool = False,
     logc: bool | None = None,
@@ -85,6 +86,8 @@ def plot(
         If ``True``, the interactive log buttons will be hidden.
     ignore_size:
         If ``True``, skip the check that prevents the rendering of very large data.
+    ignore_sorted:
+        Do not check if the coordinates are sorted before plotting.
     legend:
         Show legend if ``True``. If ``legend`` is a tuple, it should contain the
         ``(x, y)`` coordinates of the legend's anchor point in axes coordinates.
@@ -170,7 +173,13 @@ def plot(
     )
 
     nodes = input_to_nodes(
-        obj, processor=partial(preprocess, ignore_size=ignore_size, coords=coords)
+        obj,
+        processor=partial(
+            preprocess,
+            ignore_size=ignore_size,
+            ignore_sorted=ignore_sorted,
+            coords=coords,
+        ),
     )
 
     ndims = set()