Dynamically updating plot in matplotlib

Question

I am making an application in Python which collects data from a serial port and plots a graph of the collected data against arrival time  The time of arrival for the data is uncertain  I want the plot to be updated when data is received  I searched on how to do this and found two methods    Clear the plot and re-draw the plot with all the points again  Animate the plot by changing it after a particular interval    I do not prefer the first one as the program runs and collects data for a long time  a day for example   and redrawing the plot will be pretty slow  The second one is also not preferable as time of arrival of data is uncertain and I want the plot to update only when the data is received   Is there a way in which I can update the plot just by adding more points to it only when the data is received

User · Answer

Here is a way which allows to remove points after a certain number of points plotted   import matplotlib pyplot as plt   generate axes object ax   plt axes      set limits plt xlim 0 10   plt ylim 0 10   for i in range 10                  add something to axes          ax scatter  i    i         ax plot  i    i 1    rx           draw the plot      plt draw         plt pause 0 01   is necessary for the plot to update for some reason         start removing points if you don t want all shown      if i gt 2           ax lines 0  remove            ax collections 0  remove

User · Answer

Is there a way in which I can update the plot just by adding more point s  to it      There are a number of ways of animating data in matplotlib  depending on the version you have  Have you seen the matplotlib cookbook examples  Also  check out the more modern animation examples in the matplotlib documentation  Finally  the animation API defines a function FuncAnimation which animates a function in time  This function could just be the function you use to acquire your data   Each method basically sets the data property of the object being drawn  so doesn t require clearing the screen or figure  The data property can simply be extended  so you can keep the previous points and just keep adding to your line  or image or whatever you are drawing    Given that you say that your data arrival time is uncertain your best bet is probably just to do something like   import matplotlib pyplot as plt import numpy  hl    plt plot          def update line hl  new data       hl set xdata numpy append hl get xdata    new data       hl set ydata numpy append hl get ydata    new data       plt draw     Then when you receive data from the serial port just call update line

User · Answer

I know I m late to answer this question  but for your issue you could look into the  joystick  package  I designed it for plotting a stream of data from the serial port  but it works for any stream  It also allows for interactive text logging or image plotting  in addition to graph plotting   No need to do your own loops in a separate thread  the package takes care of it  just give the update frequency you wish  Plus the terminal remains available for monitoring commands while plotting  See http   www github com ceyzeriat joystick  or https   pypi python org pypi joystick  use pip install joystick to install   Just replace np random random   by your real data point read from the serial port in the code below   import joystick as jk import numpy as np import time  class test jk Joystick         initialize the infinite loop decorator      infinite loop   jk deco infinite loop        def  init self   args    kwargs                       Function called at initialization  see the doc                     self  t0   time time      initialize time         self xdata   np array  self  t0      time x-axis         self ydata   np array  0 0      fake data y-axis           create a graph frame         self mygraph   self add frame jk Graph name  test   size  500  500   pos  50  50   fmt  go-   xnpts 10000  xnptsmax 10000  xylim  None  None  0  1           infinite loop wait time 0 2      def  generate data self      function looped every 0 2 second to read or produce data                     Loop starting with the simulation start  getting data and     pushing it to the graph every 0 2 seconds                       concatenate data on the time x-axis         self xdata   jk core add datapoint self xdata  time time    xnptsmax self mygraph xnptsmax            concatenate data on the fake data y-axis         self ydata   jk core add datapoint self ydata  np random random    xnptsmax self mygraph xnptsmax          self mygraph set xydata t  self ydata   t   test   t start   t stop

User · Answer

In order to do this without FuncAnimation  eg you want to execute other parts of the code while the plot is being produced or you want to be updating several plots at the same time   calling draw alone does not produce the plot  at least with the qt backend    The following works for me   import matplotlib pyplot as plt plt ion   class DynamicUpdate         Suppose we know the x range     min x   0     max x   10      def on launch self            Set up plot         self figure  self ax   plt subplots           self lines    self ax plot         o            Autoscale on unknown axis and known lims on the other         self ax set autoscaley on True          self ax set xlim self min x  self max x           Other stuff         self ax grid                    def on running self  xdata  ydata            Update data  with the new  and  the old points          self lines set xdata xdata          self lines set ydata ydata           Need both of these in order to rescale         self ax relim           self ax autoscale view            We need to draw  and  flush         self figure canvas draw           self figure canvas flush events         Example     def   call   self           import numpy as np         import time         self on launch           xdata              ydata              for x in np arange 0 10 0 5               xdata append x              ydata append np exp -x  2  10 np exp - x-7   2               self on running xdata  ydata              time sleep 1          return xdata  ydata  d   DynamicUpdate   d

[python] Dynamically updating plot in matplotlib

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