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如何在matplotlib中绘制渐变色线?

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如何在matplotlib中绘制渐变色线?

我最近以类似的要求回答了一个问题(使用matplotlib创建了20多种独特的图例颜色)。我在那里展示了您可以映射将线条绘制到颜色图所需的颜色循环。您可以使用相同的过程为每对点获取特定的颜色。

您应该仔细选择颜色图,因为如果颜色图是彩色的,则沿线的颜色过渡可能会显得很剧烈。

或者,您可以更改每个线段的Alpha,范围从0到1。

下面的代码示例中包含一个例程(

highResPoints
),用于扩展您的随机游走的点数,因为如果您的点数太少,则过渡可能看起来很困难。我最近提供的另一个答案启发了这段代码:https
:
//stackoverflow.com/a/8253729/717357

import numpy as npimport matplotlib.pyplot as pltdef highResPoints(x,y,factor=10):    '''    Take points listed in two vectors and return them at a higher    resultion. Create at least factor*len(x) new points that include the    original points and those spaced in between.    Returns new x and y arrays as a tuple (x,y).    '''    # r is the distance spanned between pairs of points    r = [0]    for i in range(1,len(x)):        dx = x[i]-x[i-1]        dy = y[i]-y[i-1]        r.append(np.sqrt(dx*dx+dy*dy))    r = np.array(r)    # rtot is a cumulative sum of r, it's used to save time    rtot = []    for i in range(len(r)):        rtot.append(r[0:i].sum())    rtot.append(r.sum())    dr = rtot[-1]/(NPOINTS*RESFACT-1)    xmod=[x[0]]    ymod=[y[0]]    rPos = 0 # current point on walk along data    rcount = 1     while rPos < r.sum():        x1,x2 = x[rcount-1],x[rcount]        y1,y2 = y[rcount-1],y[rcount]        dpos = rPos-rtot[rcount]         theta = np.arctan2((x2-x1),(y2-y1))        rx = np.sin(theta)*dpos+x1        ry = np.cos(theta)*dpos+y1        xmod.append(rx)        ymod.append(ry)        rPos+=dr        while rPos > rtot[rcount+1]: rPos = rtot[rcount+1] rcount+=1 if rcount>rtot[-1]:     break    return xmod,ymod#ConSTANTSNPOINTS = 10COLOR='blue'RESFACT=10MAP='winter' # choose carefully, or color transitions will not appear smoooth# create random datanp.random.seed(101)x = np.random.rand(NPOINTS)y = np.random.rand(NPOINTS)fig = plt.figure()ax1 = fig.add_subplot(221) # regular resolution color mapax2 = fig.add_subplot(222) # regular resolution alphaax3 = fig.add_subplot(223) # high resolution color mapax4 = fig.add_subplot(224) # high resolution alpha# Choose a color map, loop through the colors, and assign them to the color # cycle. You need NPOINTS-1 colors, because you'll plot that many lines # between pairs. In other words, your line is not cyclic, so there's # no line from end to beginningcm = plt.get_cmap(MAP)ax1.set_color_cycle([cm(1.*i/(NPOINTS-1)) for i in range(NPOINTS-1)])for i in range(NPOINTS-1):    ax1.plot(x[i:i+2],y[i:i+2])ax1.text(.05,1.05,'Reg. Res - Color Map')ax1.set_ylim(0,1.2)# same approach, but fixed color and # alpha is scale from 0 to 1 in NPOINTS stepsfor i in range(NPOINTS-1):    ax2.plot(x[i:i+2],y[i:i+2],alpha=float(i)/(NPOINTS-1),color=COLOR)ax2.text(.05,1.05,'Reg. Res - alpha')ax2.set_ylim(0,1.2)# get higher resolution dataxHiRes,yHiRes = highResPoints(x,y,RESFACT)npointsHiRes = len(xHiRes)cm = plt.get_cmap(MAP)ax3.set_color_cycle([cm(1.*i/(npointsHiRes-1))for i in range(npointsHiRes-1)])for i in range(npointsHiRes-1):    ax3.plot(xHiRes[i:i+2],yHiRes[i:i+2])ax3.text(.05,1.05,'Hi Res - Color Map')ax3.set_ylim(0,1.2)for i in range(npointsHiRes-1):    ax4.plot(xHiRes[i:i+2],yHiRes[i:i+2],  alpha=float(i)/(npointsHiRes-1),  color=COLOR)ax4.text(.05,1.05,'High Res - alpha')ax4.set_ylim(0,1.2)fig.savefig('gradColorLine.png')plt.show()

此图显示了四种情况:



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