在图表下设置颜色图 [英] Set a colormap under a graph

问题描述

我知道这已经被很好地证明了，但是我正在努力在我的代码中实现它.

I know this is well documented, but I'm struggling to implement this in my code.

我想用一个颜色贴图在我的图形下面的区域着色.是否有可能在30多个点上都具有一种颜色，即红色，直到该点为止都有渐变?

I would like to shade the area under my graph with a colormap. Is it possible to have a colour, i.e. red from any points over 30, and a gradient up until that point?

我正在使用fill_between方法，但是如果有更好的方法可以更改它，我很乐意.

I am using the method fill_between, but I'm happy to change this if there is a better way to do it.

def plot(sd_values):

    plt.figure()
    sd_values=np.array(sd_values)
    x=np.arange(len(sd_values))
    plt.plot(x,sd_values, linewidth=1)
    plt.fill_between(x,sd_values, cmap=plt.cm.jet)
    plt.show()

这是目前的结果.我已经尝试过 axvspan ，但这没有 cmap 作为选项.为什么下图没有显示颜色图?

This is the result at the moment. I have tried axvspan, but this doesnt have cmap as an option. Why does the below graph not show a colormap?

推荐答案

我不确定 cmap 参数是否应作为 fill_between 绘图命令的一部分.在您的情况下，可能要使用 fill()命令btw.

I'm not sure if the cmap argument should be part of the fill_between plotting command. In your case probably want to use the fill() command btw.

这些填充命令创建多边形或多边形集合.多边形集合可以使用 cmap ，但是使用 fill 时，无法提供应为其着色的数据.

These fill commands create polygons or polygon collections. A polygon collection can take a cmap but with fill there is no way of providing the data on which it should be colored.

(据我所知)，当然不可能的是根据需要用渐变填充单个多边形.

What's (for as far as i know) certainly not possible is to fill a single polygon with a gradient as you wish.

下一个最好的办法是伪造它.您可以绘制阴影图像并根据创建的多边形对其进行裁剪.

The next best thing is to fake it. You can plot a shaded image and clip it based on the created polygon.

# create some sample data
x = np.linspace(0, 1)
y = np.sin(4 * np.pi * x) * np.exp(-5 * x) * 120

fig, ax = plt.subplots()

# plot only the outline of the polygon, and capture the result
poly, = ax.fill(x, y, facecolor='none')

# get the extent of the axes
xmin, xmax = ax.get_xlim()
ymin, ymax = ax.get_ylim()

# create a dummy image
img_data = np.arange(ymin,ymax,(ymax-ymin)/100.)
img_data = img_data.reshape(img_data.size,1)

# plot and clip the image
im = ax.imshow(img_data, aspect='auto', origin='lower', cmap=plt.cm.Reds_r, extent=[xmin,xmax,ymin,ymax], vmin=y.min(), vmax=30.)

im.set_clip_path(poly)

为图像提供一个范围，该范围基本上将其沿整个轴拉伸.然后clip_path使其仅显示绘制 fill 多边形的位置.

The image is given an extent which basically stretches it over the entire axes. Then the clip_path makes it only showup where the fill polygon is drawn.

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