The road to Visualization （ Twelve ）Collection Class explanation

One . brief introduction

Collection Class draws classes that share a large collection of objects that share most properties , Is the base class for all collection classes . He can't use it alone , You must subclass before you can use .

Two . Class definition

def __init__(self,
                 edgecolors=None,
                 facecolors=None,
                 linewidths=None,
                 linestyles='solid',
                 capstyle=None,
                 joinstyle=None,
                 antialiaseds=None,
                 offsets=None,
                 transOffset=None,
                 norm=None,  # optional for ScalarMappable
                 cmap=None,  # ditto
                 pickradius=5.0,
                 hatch=None,
                 urls=None,
                 offset_position='screen',
                 zorder=1,
                 **kwargs
                 ):

Parameters 1：edgecolors： Specifies the color of the edge of the color block .

Parameters 2：facecolors： Specifies the color of the color patch .

Parameters 3：linewidths： Specifies the color block lineweight .

Parameters 4：linestyles： Specifies the color block linetype .

Parameters 5：capstyle： Specifies the line brush style .

Parameters 6：joinstyle： Specify the connection style .

Parameters 7：antialiaseds： Boolean type , Specifies whether each object in the collection should be anti aliased painted .

Parameters 8：offset： Specifies the color block offset .

Parameters 9：norm： Specifies whether to normalize .

Parameters 10：cmap： Appoint colormap.

Parameters 11：pickradius： Specifies the pick radius for tightness testing .

Parameters 12：hatch： Specifies the internal hatch pattern .

Parameters 13：urls： Unknown ？

Parameters 14：offset_position： Specifies that the offset is treated as data coordinates rather than screen coordinates .

Parameters 15：zoeder： Specifies the color patch layer .

Parameters 16：**kwargs： The received keyword parameters are passed to Artist Base class .

Yes Collection Instances of its subclasses , Use get_ The attribute name () Get the corresponding property value of the current instance .

There are two ways to set properties ：

• set(**kwarg)
• set_ The attribute name ( Property value )

3、 ... and . Example

Use case insensitive in case drawing X11/CSS4 Color name . Use a scatter chart scatter function , His return value is PathCollection Is precisely Collection Subclasses of classes , Next, a scatter diagram is used to demonstrate .

3.1edgecolors

edgecolors Used to specify the edge color of the color block , If specified as None Then use matplotlib.rcParams Internally determined value .

The colors you can use are shown in the link below ：

matplotlib Color Introduction

In the original drawing, only linewidth Parameters and facecolor Parameters , So the marker point will only have one color .

import matplotlib.pyplot as plt

import numpy as np

plt.rcParams['font.sans-serif'] = ['SimHei']  #  Settings support Chinese 
plt.rcParams['axes.unicode_minus'] = False  #  Set up - Number 
plt.style.use('ggplot')

x = np.arange(15)
y = 2 * x + np.random.randint(-1, 5, size=15)

collection = plt.scatter(x, y, linewidths=4, s=8*(x+y), facecolor="blue", label=' Example scatter plot ')

plt.legend()
plt.title(" Original picture ", fontsize=25, fontweight="bold")
plt.show()

The original effect ：

Add a statement collection.set_edgecolor('mediumseagreen') Specify the edge color , The effect is as follows ：

linewidth Parameters and edgecolor The two parameters should cooperate with each other to achieve the real effect . The color of one of the marks cannot be set separately .

You can pass an entire color sequence to set the edge color of multiple points , The sequence length does not have to be the same as the number of points , By default, the colors in the sequence are recycled , The effect is as follows ：

3.2facecolors

facecolors Used to specify the surface color of the color block , If specified as None Then use matplotlib.rcParams Internally determined value . See for color details 3.1.

Use set() Method to set a new surface color

collection.set(facecolor="gray")

Same as edgecolor Same parameter , You can set the cycle color , The effect is as follows ：

3.3linewidths

linewidths Parameter specifies the edge lineweight , You can specify a scalar or a scalar sequence . Use set_linewidth Method to set , In addition to the two common setting methods, you can also use simplified statements set_lw Method to set .

The new original image is as follows ：

import matplotlib.pyplot as plt

import numpy as np

plt.rcParams['font.sans-serif'] = ['SimHei']  #  Settings support Chinese 
plt.rcParams['axes.unicode_minus'] = False  #  Set up - Number 
plt.style.use('ggplot')

x = np.arange(15)
y = 2 * x + np.random.randint(-1, 5, size=15)

collection = plt.scatter(x, y, linewidths=4, s=8*(x+y), edgecolors="cyan", facecolor="blue", label=' Example scatter plot ')
collection.set_lw(8)

plt.legend()
plt.title(" Original picture ", fontsize=25, fontweight="bold")
plt.show()

The effect is as follows ：

3.4capstyle

capstyle Parameter is used to set the style of both ends of the line , For details, see

capstyle Parameters,

3.5joinstyle

joinstyle Parameter is used to set the connection mode of two line segments , For details, see

joinstyle Parameters,

3.6antialiaseds

antialiaseds Parameter is used to set whether anti aliasing is used for painting . The adjustment of this parameter has no obvious visual effect .

3.7cmap

cmap Used to specify the color mapping table . This place needs attention , If you want to use it cmap The mapping table , The mapping method must be specified , Using the mapping table takes precedence over directly specifying the specific surface color , The edge color will not be affected .

import matplotlib.pyplot as plt

import numpy as np

plt.rcParams['font.sans-serif'] = ['SimHei']  #  Settings support Chinese 
plt.rcParams['axes.unicode_minus'] = False  #  Set up - Number 
plt.style.use('ggplot')

x = np.arange(15)
y = 2 * x + np.random.randint(-1, 5, size=15)

collection = plt.scatter(x, y, linewidths=4, s=8*(x+y), c=2*(x+y), edgecolors="cyan", facecolor="blue", label=' Example scatter plot ')
collection.set_cmap("PuOr")

plt.legend()
plt.title(" Original picture ", fontsize=25, fontweight="bold")
plt.show()

The effect is as follows ：

3.8hatch

hatch Parameter is used to set the hatch pattern , Optional ：

/ - diagonal hatching

\ - back diagonal

| - vertical

+ - crossed

- - horizontal
x - crossed diagonal

o - small circle

O - large circle

. - dots

* - stars、

Pay attention to some points. , The first letter can be combined , If the same letter repeats , Will increase the shadow density of the pattern . Second, shadows are different from other attributes , Only... Can be specified for the entire collection , Instead, you cannot specify... For each member individually .

Use o To add shadows , The effect is as follows ：

Use ooo To increase shadow density , The effect is as follows ：

Use ox* To combine shadows , The effect is as follows ：

The color of the shadow and edgecolor Set the same color , Changing the edge line color can also affect the shadow color , The effect is as follows ：

3.9linestyles

linestyles Parameter is used to set the edge line style , See the link below for details ：

linestyle Parameters,

Change the line style to dotted line , The effect is as follows ：

3.10alpha

alpha Parameter is often used to set the transparency of painted objects ,0-1 Value between . The effect is as follows ：