【ROS学习】ROS-kinetic 中运行 rqt_plot 的报错：numpy.linalg.LinAlgError: Singular matrix

一、问题描述

自己在调试 ROS 程序的时候，运行 rqt_plot 报错：

/usr/lib/python2.7/dist-packages/matplotlib/axis.py:1015: UserWarning: Unable to find pixel distance along axis for interval padding of ticks; assuming no interval padding needed.
  warnings.warn("Unable to find pixel distance along axis "
/usr/lib/python2.7/dist-packages/matplotlib/axis.py:1025: UserWarning: Unable to find pixel distance along axis for interval padding of ticks; assuming no interval padding needed.
  warnings.warn("Unable to find pixel distance along axis "
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_plot/data_plot/mat_data_plot.py", line 107, in resizeEvent
    self.figure.tight_layout()
  File "/usr/lib/python2.7/dist-packages/matplotlib/figure.py", line 1754, in tight_layout
    rect=rect)
  File "/usr/lib/python2.7/dist-packages/matplotlib/tight_layout.py", line 349, in get_tight_layout_figure
    pad=pad, h_pad=h_pad, w_pad=w_pad)
  File "/usr/lib/python2.7/dist-packages/matplotlib/tight_layout.py", line 128, in auto_adjust_subplotpars
    fig.transFigure.inverted())
  File "/usr/lib/python2.7/dist-packages/matplotlib/transforms.py", line 1775, in inverted
    self._inverted = Affine2D(inv(mtx), shorthand_name=shorthand_name)
  File "/usr/local/lib/python2.7/dist-packages/numpy/linalg/linalg.py", line 551, in inv
    ainv = _umath_linalg.inv(a, signature=signature, extobj=extobj)
  File "/usr/local/lib/python2.7/dist-packages/numpy/linalg/linalg.py", line 97, in _raise_linalgerror_singular
    raise LinAlgError("Singular matrix")
numpy.linalg.LinAlgError: Singular matrix
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二、解决方法

方法一：暂时解决问题

在终端先运行

rqt
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会弹出一个空白的界面：

然后在桌面的最上端，选择
Plugins->Visualization->Plot

然后就可以显示 rqt_plot 界面了~~~~

方法二：永久解决问题

在Matplotlib官网可以发现，kinetic中的python2.7和Matplotlib是不兼容的，并且不再支持Python2。
所以我们可以安装 另一个可视化工具，PyQtGraph。
运行如下指令：

pip install pyqtgraph
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或者官网下载安装包安装。

然后再次运行

rqt_plot
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就可以愉快地使用 rqt_plot 啦~~~~~~~~

参考链接：
[1] ROS入门笔记（五）：ROS中运行rqt_plot的问题（kinetic） https://www.cnblogs.com/IT-cute/p/13122280.html
[2] ROS入门：rqt_plot出现错误：UserWarning: Unable to find pixel distance along axis for interval padding of tic-- https://blog.csdn.net/qinqinxiansheng/article/details/106736892