exp show: Add parallel coordinates plot.

Uses `TabularData.to_parallel_coordinates`.
Adds new arguments: `html`, `color-by`, `out`, `open`

Closes #4455

dvc/command/experiments.py

@@ -3,6 +3,7 @@
 from collections import Counter, OrderedDict, defaultdict
 from datetime import date, datetime
 from fnmatch import fnmatch
+from pathlib import Path
 from typing import TYPE_CHECKING, Dict, Iterable, Optional
 
 from funcy import compact, lmap
@@ -387,6 +388,7 @@ def show_experiments(
     no_timestamp=False,
     csv=False,
     markdown=False,
+    html=False,
     **kwargs,
 ):
     from funcy.seqs import flatten as flatten_list
@@ -474,6 +476,18 @@ def show_experiments(
     if kwargs.get("only_changed", False):
         td.drop_duplicates("cols")
 
+    extra_render_args = {}
+    if html:
+        td.dropna("rows")
+        td.column("Experiment")[:] = [
+            # remove tree characters
+            str(x).encode("ascii", "ignore").strip().decode()
+            for x in td.column("Experiment")
+        ]
+        rel = kwargs.get("out") or "dvc_plots"
+        extra_render_args["output_path"] = (Path.cwd() / rel).resolve()
+        extra_render_args["color_by"] = kwargs.get("color_by", "Experiment")
+
     td.render(
         pager=pager,
         borders=True,
@@ -482,8 +496,26 @@ def show_experiments(
         row_styles=row_styles,
         csv=csv,
         markdown=markdown,
+        html=html,
+        **extra_render_args,
     )
 
+    if html and kwargs.get("open"):
+        import webbrowser
+        from platform import uname
+
+        if "Microsoft" in uname().release:
+            url = Path(rel) / "index.html"
+        else:
+            url = Path(extra_render_args["output_path"]) / "index.html"
+            url = url.as_uri()
+
+        opened = webbrowser.open(url)
+
+        if not opened:
+            ui.error_write("Failed to open. Please try opening it manually.")
+            return 1
+
 
 def _normalize_headers(names, count):
     return [
@@ -525,6 +557,10 @@ def run(self):
             fill_value = "" if self.args.csv else FILL_VALUE
             iso = True if self.args.csv else False
 
+            if self.args.html:
+                self.args.only_changed = True
+                self.args.no_timestamp = True
+
             show_experiments(
                 all_experiments,
                 include_metrics=self.args.include_metrics,
@@ -541,6 +577,10 @@ def run(self):
                 csv=self.args.csv,
                 markdown=self.args.markdown,
                 only_changed=self.args.only_changed,
+                html=self.args.html,
+                color_by=self.args.color_by,
+                out=self.args.out,
+                open=self.args.open,
             )
         return 0
 
@@ -1045,6 +1085,34 @@ def add_parser(subparsers, parent_parser):
             "across the selected experiments."
         ),
     )
+    experiments_show_parser.add_argument(
+        "--html",
+        action="store_true",
+        default=False,
+        help="Generate a parallel coordinates plot from the tabulated output.",
+    )
+    experiments_show_parser.add_argument(
+        "--color-by",
+        default="Experiment",
+        help=(
+            "Use the specified metric or param as color in "
+            "the parallel coordinates plot."
+        ),
+        metavar="<metric/param>",
+    )
+    experiments_show_parser.add_argument(
+        "-o",
+        "--out",
+        default=None,
+        help="Destination path to save the parallel coordinates plot to",
+        metavar="<path>",
+    ).complete = completion.DIR
+    experiments_show_parser.add_argument(
+        "--open",
+        action="store_true",
+        default=False,
+        help="Open the parallel coordinates plot directly in the browser.",
+    )
     experiments_show_parser.set_defaults(func=CmdExperimentsShow)
 
     EXPERIMENTS_APPLY_HELP = (

tests/func/experiments/test_show.py

@@ -582,3 +582,76 @@ def test_show_only_changed(tmp_dir, dvc, scm, capsys):
     cap = capsys.readouterr()
 
     assert "bar" not in cap.out
+
+
+def test_show_parallel_coordinates(tmp_dir, dvc, scm, mocker):
+    from dvc.command import experiments
+
+    webbroser_open = mocker.patch("webbrowser.open")
+    show_experiments = mocker.spy(experiments, "show_experiments")
+
+    tmp_dir.gen("copy.py", COPY_SCRIPT)
+    params_file = tmp_dir / "params.yaml"
+    params_data = {
+        "foo": 1,
+        "bar": 1,
+    }
+    (tmp_dir / params_file).dump(params_data)
+
+    dvc.run(
+        cmd="python copy.py params.yaml metrics.yaml",
+        metrics_no_cache=["metrics.yaml"],
+        params=["foo", "bar"],
+        name="copy-file",
+        deps=["copy.py"],
+    )
+    scm.add(
+        [
+            "dvc.yaml",
+            "dvc.lock",
+            "copy.py",
+            "params.yaml",
+            "metrics.yaml",
+            ".gitignore",
+        ]
+    )
+    scm.commit("init")
+
+    dvc.experiments.run(params=["foo=2"])
+
+    assert main(["exp", "show", "--html"]) == 0
+    kwargs = show_experiments.call_args[1]
+
+    assert kwargs["only_changed"]
+    assert kwargs["no_timestamp"]
+    assert kwargs["color_by"] == "Experiment"
+    html_text = (tmp_dir / "dvc_plots" / "index.html").read_text()
+
+    assert all(rev in html_text for rev in ["workspace", "master", "[exp-"])
+
+    assert (
+        '{"label": "metrics.yaml:foo", "values": [2.0, 1.0, 2.0]}' in html_text
+    )
+    assert (
+        '{"label": "params.yaml:foo", "values": [2.0, 1.0, 2.0]}' in html_text
+    )
+    assert '"line": {"color": [0, 1, 2]' in html_text
+
+    assert (
+        main(["exp", "show", "--html", "--color-by", "metrics.yaml:foo"]) == 0
+    )
+    kwargs = show_experiments.call_args[1]
+
+    assert kwargs["color_by"] == "metrics.yaml:foo"
+    html_text = (tmp_dir / "dvc_plots" / "index.html").read_text()
+    assert '"line": {"color": [2.0, 1.0, 2.0]' in html_text
+
+    assert main(["exp", "show", "--html", "--out", "experiments"]) == 0
+    kwargs = show_experiments.call_args[1]
+
+    assert kwargs["out"] == "experiments"
+    assert (tmp_dir / "experiments" / "index.html").exists()
+
+    assert main(["exp", "show", "--html", "--open"]) == 0
+
+    webbroser_open.assert_called()

tests/unit/command/test_experiments.py

@@ -613,3 +613,37 @@ def test_experiments_init_config(dvc, mocker):
         "live": "dvclive",
     }
     assert m.call_args[1]["overrides"] == {"cmd": "cmd"}
+
+
+def test_show_experiments_html(tmp_dir, mocker):
+    all_experiments = {
+        "workspace": {
+            "baseline": {
+                "data": {
+                    "timestamp": None,
+                    "params": {"params.yaml": {"data": {"foo": 1}}},
+                    "queued": False,
+                    "running": False,
+                    "executor": None,
+                    "metrics": {
+                        "scores.json": {"data": {"bar": 0.9544670443829399}}
+                    },
+                }
+            }
+        },
+    }
+    experiments_table = mocker.patch(
+        "dvc.command.experiments.experiments_table"
+    )
+    td = experiments_table.return_value
+
+    show_experiments(all_experiments, html=True)
+
+    td.dropna.assert_called_with("rows")
+
+    render_kwargs = td.render.call_args[1]
+
+    for arg in ["html", "output_path", "color_by"]:
+        assert arg in render_kwargs
+    assert render_kwargs["output_path"] == tmp_dir / "dvc_plots"
+    assert render_kwargs["color_by"] == "Experiment"