The plot will autoscale base on the data that has been plotted to it. In your code, you are repeatedly calling plot(), albeit with a "scrolled" version of the data, but all of the previous calls to plot() are still visible. Also, no x-coordinate information is provided to the calls to plot(), so each new call to plot() only overlays on top of the previous calls.
I also see that you are using the interactive mode. This isn't really necessary. I would suggest reading through some of the animation examples to see how to automatically update your plot: http://matplotlib.org/examples/animation/index.html . I would particularly point out the "animate_decay" example. While it isn't a scrolling example, you can see how to update an existing plot with new data from a generator. It would then just be a matter of updating the x-limits for each update. I hope that helps! Ben Root On Wed, Jun 3, 2015 at 12:17 PM, Alejandro Ureta < alejandro.r.ur...@gmail.com> wrote: > Hi, I am trying to get a live scrolling graph built from data send by two > arduino sensors. Although live data is being shown in the graph I am not > able to get it scrolling. The arduino and Python codes I am working with > are included below. I would very much appreciate if you can help me getting > the scrolling graph working. > > > > PYTHON CODE: > > import serial # import Serial Library > > import numpy # Import numpy > > import matplotlib.pyplot as plt #import matplotlib library > > from drawnow import * > > > > tempF= [] > > pressure= [] > > > > arduinoData = serial.Serial('com6', 115200) #Creating our serial object > named arduinoData > > plt.ion() #Tell matplotlib you want interactive mode to plot live data > > cnt=0 > > > > def makeFig(): #Create a function that makes our desired plot > > plt.ylim(0,500) #Set y min and max > values > > plt.title('Frequency vs Time') #Plot the title > > plt.grid(True) #Turn the grid on > > plt.ylabel('Frequency (pulses/sec)') #Set > ylabels > > plt.plot(tempF, 'ro-', label='pulses/sec') #plot the temperature > > plt.legend(loc='upper left') #plot the legend > > > > > > plt2=plt.twinx() #Create a second y axis > > plt.ylim(0,500) #Set limits of second y > axis- adjust to readings you are getting > > plt2.plot(pressure, 'b^-', label='Pressure (Pa)') #plot pressure data > > plt2.set_ylabel('Pressrue (Pa)') #label second y > axis > > plt2.ticklabel_format(useOffset=False) #Force matplotlib to > NOT autoscale y axis > > plt2.legend(loc='upper right') #plot the legend > > > > > > while True: # While loop that loops forever > > while (arduinoData.inWaiting()==0): #Wait here until there is data > > pass #do nothing > > arduinoString = arduinoData.readline() #read the line of text from the > serial port > > dataArray = arduinoString.split(',') #Split it into an array called > dataArray > > temp = float(dataArray[0]) #Convert first element to > floating number and put in temp > > pres = float(dataArray[1]) #Convert second element to > floating number and put in P > > tempF.append(temp) #Build our tempF array by > appending temp readings > > pressure.append(pres) #Building our pressure > array by appending P readings > > drawnow(makeFig) #Call drawnow to update our > live graph > > plt.pause(.000001) #Pause Briefly. Important to > keep drawnow from crashing > > cnt=cnt+1 > > if(cnt>10): #If you have 50 or more points, > delete the first one from the array > > tempF.pop(0) #This allows us to just see the > last 50 data points > > pressure.pop(0) > > > > > > > > > > > > > > > > ARDUINO CODE: > > > > > > #include "Wire.h" // imports the wire library for talking over I2C > > #include "Adafruit_BMP085.h" // import the Pressure Sensor Library > > Adafruit_BMP085 mySensor; // create sensor object called mySensor > > > > float tempC; // Variable for holding temp in C > > float tempF; // Variable for holding temp in F > > float pressure; //Variable for holding pressure reading > > > > void setup(){ > > Serial.begin(115200); //turn on serial monitor > > mySensor.begin(); //initialize mySensor > > } > > > > void loop() { > > tempC = mySensor.readTemperature(); // Be sure to declare your variables > > tempF = tempC*1.8 + 32.; // Convert degrees C to F > > pressure=mySensor.readPressure(); //Read Pressure > > > > > > Serial.print(tempF); > > Serial.print(" , "); > > Serial.println(pressure); > > delay(250); //Pause between readings. > > } > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users > >
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