matplotlib库学习(一)

matplotlib库是python中实现数据处理与展示的非常优秀的类库， 它提供了超过100多种的图像处理和现实方法 可以说是非常强大了

我们来看看这个函数：

import tensorflow as tf 
import numpy as np 
import matplotlib.pyplot as plt 

train_X = np.linspace(-1, 1, 100) # x 从-1 ~ 1 均匀分布100个样本，默认包括start&endpoint
train_Y = 2 * train_X + np.random.randn(*train_X.shape) * 0.3

plt.plot(train_X, train_Y, 'ro', label = "Original data")#Plot y versus x as lines and/or markers.

plt.plot这句有很强的拓展性，可以根据不同的参数刻画出不同的图像

下面我们来看看这些参数：

train_x : x

train_y: y

The coordinates of the points or line nodes are given by x, y.

x,y 还可以通过标签给定：

使用方法如下：

 plot('xlabel', 'ylabel', data=obj)# obj['xlabel'] 

All indexable objects are supported. This could e.g. be a dict, a pandas.DataFame or a structured numpy array.

当要绘制多组x, y， 我们可以这样给定参数：

• The most straight forward way is just to call plot multiple times.
  Example:

    >>> plot(x1, y1, 'bo')
    >>> plot(x2, y2, 'go')
  

• Alternatively, if your data is already a 2d array, you can pass it
  directly to x, y. A separate data set will be drawn for every
  column.

     Example: an array ``a`` where the first column represents the *x*
     values and the other columns are the *y* columns::
  
     >>> plot(a[0], a[1:])
  

• The third way is to specify multiple sets of [x], y, [fmt]
  groups::

      >>> plot(x1, y1, 'g^', x2, y2, 'g-')
  
      In this case, any additional keyword argument applies to all
      datasets. Also this syntax cannot be combined with the *data*
      parameter.
  

‘ro’ : fmt

The optional parameter fmt is a convenient way for defining basic formatting like color, marker and linestyle.

让我们看具体了解一下这个参数；

"""
Notes
        -----
        **Format Strings**

        A format string consists of a part for color, marker and line::

            fmt = '[color][marker][line]'

        Each of them is optional. If not provided, the value from the style
        cycle is used. Exception: If ``line`` is given, but no ``marker``,
        the data will be a line without markers.

        **Colors**

        The following color abbreviations are supported:

        =============    ===============================
        character        color
        =============    ===============================
        ``'b'``          blue
        ``'g'``          green
        ``'r'``          red
        ``'c'``          cyan
        ``'m'``          magenta
        ``'y'``          yellow
        ``'k'``          black
        ``'w'``          white
        =============    ===============================

        If the color is the only part of the format string, you can
        additionally use any  `matplotlib.colors` spec, e.g. full names
        (``'green'``) or hex strings (``'#008000'``).

        **Markers**

        =============    ===============================
        character        description
        =============    ===============================
        ``'.'``          point marker
        ``','``          pixel marker
        ``'o'``          circle marker
        ``'v'``          triangle_down marker
        ``'^'``          triangle_up marker
        ``'<'``          triangle_left marker
        ``'>'``          triangle_right marker
        ``'1'``          tri_down marker
        ``'2'``          tri_up marker
        ``'3'``          tri_left marker
        ``'4'``          tri_right marker
        ``'s'``          square marker
        ``'p'``          pentagon marker
        ``'*'``          star marker
        ``'h'``          hexagon1 marker
        ``'H'``          hexagon2 marker
        ``'+'``          plus marker
        ``'x'``          x marker
        ``'D'``          diamond marker
        ``'d'``          thin_diamond marker
        ``'|'``          vline marker
        ``'_'``          hline marker
        =============    ===============================

        **Line Styles**

        =============    ===============================
        character        description
        =============    ===============================
        ``'-'``          solid line style
        ``'--'``         dashed line style
        ``'-.'``         dash-dot line style
        ``':'``          dotted line style
        =============    ===============================
"""

eg:

""" 
        Example format strings::

            'b'    # blue markers with default shape
            'ro'   # red circles
            'g-'   # green solid line
            '--'   # dashed line with default color
            'k^:'  # black triangle_up markers connected by a dotted line
"""

还有一种控制 appearance 的方法 ：

"""
   You can use `.Line2D` properties as keyword arguments for more
        control on the  appearance. Line properties and *fmt* can be mixed.
        The following two calls yield identical results:

        >>> plot(x, y, 'go--', linewidth=2, markersize=12)
        >>> plot(x, y, color='green', marker='o', linestyle='dashed',
                linewidth=2, markersize=12)
"""

值得注意的是， 当两者有冲突的时候， 后者占主导地位