plotting real time data

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There are many tools to plot.

- rqt_plot

- rqt_multiplot (from ethz) tool is quite nice to use (compared to rqt_plot)

-plot_juggler this is my favourite tool its so fast plotting data and so easy to use! Try it yourself!

Install:

sudo apt-get install ros-kinetic-plotjuggler

Run it:

• rosrun plotjuggler PlotJuggler
• Go to streaming and start ros_topic_streaming
• simply select your topics you wanna stream

Start in launch file:

<!-- start plotjuggler -->
<node pkg="plotjuggler" type="PlotJuggler" name="my_plot_Juggler" args="" />

If anyone knows how to start from launch file a saved layout.xml Would be great for sharing :)

I did liveplotting in the past in two ways:

Your prefered way is the matplotlib so thats pretty easy and I explain a little bit more:

There you need a animation.FuncAnimation. It makes an animation by repeatedly calling a function/method. You can read more here.

Furter in the repeatedly called function you should do something like:

xdata.append(frame)
ydata.append(np.sin(frame))
ln.set_data(xdata, ydata)

so there you append new data and than set it. What you now need to do different is that you setup a ROS Subscriber to your data you want to publish and in the callback function/method you need to append the new data and just set in the repeatedly called function the new data. Thats only a close look about how you can do it to give you an idea.

The other way is using c++ and writing for example a rviz plugin with QT. I prefere here the QCustomPlot for live plotting. But thats a little bit tricky and needs more time when you have no idea about QT. But for me it generates better looking plots and when you are used to it its very easy too.

When you need further help please ask! It isnt too detailed. Just to give you an idea.

Since this is an old post and still seems to be active in the community, I am going to provide an example, in general, how can we do real-time plotting. Here I used matplotlib FuncAnimation function.

import matplotlib.pyplot as plt
import rospy
import tf
from nav_msgs.msg import Odometry
from tf.transformations import quaternion_matrix
import numpy as np
from matplotlib.animation import FuncAnimation


class Visualiser:
    def __init__(self):
        self.fig, self.ax = plt.subplots()
        self.ln, = plt.plot([], [], 'ro')
        self.x_data, self.y_data = [] , []

    def plot_init(self):
        self.ax.set_xlim(0, 10000)
        self.ax.set_ylim(-7, 7)
        return self.ln

    def getYaw(self, pose):
        quaternion = (pose.orientation.x, pose.orientation.y, pose.orientation.z,
                pose.orientation.w)
        euler = tf.transformations.euler_from_quaternion(quaternion)
        yaw = euler[2] 
        return yaw   

    def odom_callback(self, msg):
        yaw_angle = self.getYaw(msg.pose.pose)
        self.y_data.append(yaw_angle)
        x_index = len(self.x_data)
        self.x_data.append(x_index+1)

    def update_plot(self, frame):
        self.ln.set_data(self.x_data, self.y_data)
        return self.ln


rospy.init_node('lidar_visual_node')
vis = Visualiser()
sub = rospy.Subscriber('/dji_sdk/odometry', Odometry, vis.odom_callback)

ani = FuncAnimation(vis.fig, vis.update_plot, init_func=vis.plot_init)
plt.show(block=True)

I would recommend rqt_plot. Don't forget you can plot the std_msgs. Almost anything can be represented by them. It sounds like what you want to plot can be a Float32 message.

Also, click on the green checkmark on the rqt_plot gui above the plot area to access the axis max/min settings.