8000 Simplify `colored_line()` implementation in Multicolored lines example by 34j · Pull Request #29954 · matplotlib/matplotlib · GitHub
[go: up one dir, main page]
Skip to content

Simplify colored_line() implementation in Multicolored lines example #29954

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Apr 22, 2025
Merged

Simplify colored_line() implementation in Multicolored lines example #29954

Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
47e4a69
refactor: simplify `colored_line()` implementation in Multicolored li…
34j Apr 21, 2025
10d30a7
fix: fix based on review
34j Apr 22, 2025
05c622b
style: update multicolored_line.py
34j Apr 22, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
65 changes: 31 additions & 34 deletions galleries/examples/lines_bars_and_markers/multicolored_line.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@
from matplotlib.collections import LineCollection


def colored_line(x, y, c, ax, **lc_kwargs):
def colored_line(x, y, c, ax=None, scalex=True, scaley=True, **lc_kwargs):
"""
Plot a line with a color specified along the line by a third value.

Expand All @@ -36,9 +36,12 @@ def colored_line(x, y, c, ax, **lc_kwargs):
The horizontal and vertical coordinates of the data points.
c : array-like
The color values, which should be the same size as x and y.
ax : Axes
Axis object on which to plot the colored line.
**lc_kwargs
ax : matplotlib.axes.Axes, optional
The axes to plot on. If not provided, the current axes will be used.
scalex, scaley : bool
These parameters determine if the view limits are adapted to the data limits.
The values are passed on to autoscale_view.
**lc_kwargs : Any
Any additional arguments to pass to matplotlib.collections.LineCollection
constructor. This should not include the array keyword argument because
that is set to the color argument. If provided, it will be overridden.
Expand All @@ -49,36 +52,35 @@ def colored_line(x, y, c, ax, **lc_kwargs):
The generated line collection representing the colored line.
"""
if "array" in lc_kwargs:
warnings.warn('The provided "array" keyword argument will be overridden')
warnings.warn(
'The provided "array" keyword argument will be overridden',
UserWarning,
stacklevel=2,
)

# Default the capstyle to butt so that the line segments smoothly line up
default_kwargs = {"capstyle": "butt"}
default_kwargs.update(lc_kwargs)

# Compute the midpoints of the line segments. Include the first and last points
# twice so we don't need any special syntax later to handle them.
x = np.asarray(x)
y = np.asarray(y)
x_midpts = np.hstack((x[0], 0.5 * (x[1:] + x[:-1]), x[-1]))
y_midpts = np.hstack((y[0], 0.5 * (y[1:] + y[:-1]), y[-1]))

# Determine the start, middle, and end coordinate pair of each line segment.
# Use the reshape to add an extra dimension so each pair of points is in its
# own list. Then concatenate them to create:
# [
# [(x1_start, y1_start), (x1_mid, y1_mid), (x1_end, y1_end)],
# [(x2_start, y2_start), (x2_mid, y2_mid), (x2_end, y2_end)],
xy = np.stack((x, y), axis=-1)
xy_mid = np.concat(
(xy[0, :][None, :], (xy[:-1, :] + xy[1:, :]) / 2, xy[-1, :][None, :]), axis=0
)
segments = np.stack((xy_mid[:-1, :], xy, xy_mid[1:, :]), axis=-2)
# Note that segments is [
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This comment is really confusing, and I don't think is correct, but certainly possible I am just confused. Segments should each be [0.5 * (xy[j-1] + xy[j]), xy[j], 0.5 * (xy[j] + xy[j+1])]?

# [[x[0], y[0]], [x[0], y[0]], [mean(x[0], x[1]), mean(y[0], y[1])]],
# [[mean(x[0], x[1]), mean(y[0], y[1])], [x[1], y[1]],
# [mean(x[1], x[2]), mean(y[1], y[2])]],
# ...
# [[mean(x[-2], x[-1]), mean(y[-2], y[-1])], [x[-1], y[-1]], [x[-1], y[-1]]]
# ]
coord_start = np.column_stack((x_midpts[:-1], y_midpts[:-1]))[:, np.newaxis, :]
coord_mid = np.column_stack((x, y))[:, np.newaxis, :]
coord_end = np.column_stack((x_midpts[1:], y_midpts[1:]))[:, np.newaxis, :]
segments = np.concatenate((coord_start, coord_mid, coord_end), axis=1)

lc = LineCollection(segments, **default_kwargs)
lc.set_array(c) # set the colors of each segment
lc_kwargs["array"] = c
lc = LineCollection(segments, **lc_kwargs)

# Plot the line collection to the axes
ax = ax or plt.gca()
ax.add_collection(lc)
ax.autoscale_view(scalex=scalex, scaley=scaley)

return ax.add_collection(lc)
# Return the LineCollection object
return lc


# -------------- Create and show plot --------------
Expand All @@ -93,11 +95,6 @@ def colored_line(x, y, c, ax, **lc_kwargs):
lines = colored_line(x, y, color, ax1, linewidth=10, cmap="plasma")
fig1.colorbar(lines) # add a color legend

# Set the axis limits and tick positions
ax1.set_xlim(-1, 1)
ax1.set_ylim(-1, 1)
ax1.set_xticks((-1, 0, 1))
ax1.set_yticks((-1, 0, 1))
ax1.set_title("Color at each point")

plt.show()
Expand Down
0