兩天來，我試圖繪制一條多色線。我的資料如下所示：
gradient result
date
2022-04-15 09:43:20 0.206947 E
2022-04-15 10:25:00 0.102620 E
2022-04-15 11:06:40 0.019450 C
2022-04-15 11:48:20 0.025945 D
2022-04-15 12:30:00 0.022455 D
... ...
2022-05-02 14:13:20 0.003770 A
2022-05-02 14:55:00 0.084120 E
2022-05-02 15:36:40 0.134970 E
2022-05-02 16:18:20 0.261385 E
2022-05-02 17:00:00 0.955833 NaN
我已經習慣了以下腳本來繪制圖表：
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np
from matplotlib.collections import LineCollection
dates = data_646_mean.index
y = data_646_mean.gradient
s = pd.Series(y, index=dates)
fig, ax = plt.subplots()
#convert dates to numbers first
inxval = mdates.date2num(s.index.to_pydatetime())
points = np.array([inxval, s.values]).T.reshape(-1,1,2)
segments = np.concatenate([points[:-1],points[1:]], axis=1)
lc = LineCollection(segments, cmap="plasma", linewidth=3)
# set color to date values
#lc.set_array(inxval)
# note that you could also set the colors according to y values
lc.set_array(s.values())
# add collection to axes
ax.add_collection(lc)
ax.xaxis.set_major_locator(mdates.MonthLocator())
ax.xaxis.set_minor_locator(mdates.DayLocator())
monthFmt = mdates.DateFormatter("%b")
ax.xaxis.set_major_formatter(monthFmt)
ax.autoscale_view()
plt.show()
這已經奏效，但不同的顏色沒有設定在 y 的特定范圍內：
我真的很想讓顏色取決于結果列中的類別。如果這是不可能的，我想給出一定的間隔：
blue = 0.1 - 0.2
red = 0.2 - 0.5
green = 0.5 - 0.9
black = 0.9 1.4
我希望有人能幫助我。
uj5u.com熱心網友回復：
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np
from matplotlib.collections import LineCollection
import matplotlib.cm as cm
data_646_mean = pd.read_csv("path/to/file")
data_646_mean["date"] = pd.to_datetime(data_646_mean["date"])
dates = data_646_mean["date"].values
y = data_646_mean["gradient"].values
# convert results to categories so that we can apply it
# to the color value of the line
cat_series = pd.Categorical(data_646_mean["result"])
fig, ax = plt.subplots()
# convert dates to numbers first
dates_num = mdates.date2num(dates)
points = np.array([dates_num, y]).T.reshape(-1,1,2)
segments = np.concatenate([points[:-1],points[1:]], axis=1)
# use a subset of Tab10 (categorical color map)
cmap = cm.get_cmap('tab10', len(cat_series.categories))
lc = LineCollection(segments, cmap=cmap, linewidth=3)
lc.set_array(cat_series.codes)
ax.add_collection(lc)
# add a colorbar, modify the position of the ticks
cb = fig.colorbar(lc, ticks=np.linspace(-0.5, 3.5, 5))
# set the categories to be the value of the ticks
cb.ax.set_yticklabels(cat_series.categories)
ax.xaxis.set_major_locator(mdates.MonthLocator())
ax.xaxis.set_minor_locator(mdates.DayLocator())
monthFmt = mdates.DateFormatter("%b")
ax.xaxis.set_major_formatter(monthFmt)
ax.autoscale_view()
plt.show()
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標籤：Python matplotlib 阴谋 颜色 间隔
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