How to simplify plotting using a function?

clear all; close all;
a = arduino('COM4', 'Uno');
disp 'Connection received!'
pause (3);
figure
h = animatedline;
ax = gca;
ax.YGrid = 'on';
ax.YLim = [2.4 3.8];
title('Moisture Sensor Voltage vs Time (live)');
xlabel('Time [HH:MM:SS]');
ylabel('Voltage [volt]');
stop = false;
startTime = datetime('now');
while ~stop
   voltage = readVoltage(a, 'A1');
   t = datetime('now') - startTime;
   addpoints(h,datenum(t),voltage)
   ax.XLim = datenum([t-seconds(15) t]);
   datetick('x','keeplimits')
   drawnow
   while (voltage < 2.9)
       voltage = readVoltage(a, 'A1');
       t = datetime('now') - startTime;
       addpoints(h,datenum(t),voltage)
       ax.XLim = datenum([t-seconds(15) t]);
       datetick('x','keeplimits')
       drawnow
   end
   while (voltage > 2.9)
       writeDigitalPin(a,'D2',1);
       disp 'Pump is on!'
       voltage = readVoltage(a, 'A1');
       t = datetime('now') - startTime;
       addpoints(h,datenum(t),voltage)
       ax.XLim = datenum([t-seconds(15) t]);
       datetick('x','keeplimits')
       drawnow
       if (voltage < 2.9)
           writeDigitalPin(a,'D2',0)
           disp 'Pump is off!'
           while (voltage < 2.9)
               voltage = readVoltage(a, 'A1');
               t = datetime('now') - startTime;
               addpoints(h,datenum(t),voltage)
               ax.XLim = datenum([t-seconds(15) t]);
               datetick('x','keeplimits')
               drawnow
           end
       end
   end
end

Notice how I repeat the following lines over and over again?

   voltage = readVoltage(a, 'A1');
   t = datetime('now') - startTime;
   addpoints(h,datenum(t),voltage)
   ax.XLim = datenum([t-seconds(15) t]);
   datetick('x','keeplimits')
   drawnow

How can I simplify this code so that I don't need to repeat all 6 lines every loop and can call a function to do it.

[Peter Perkins]

Slightly off-topic: not clear to me that you need to use the old datenum format for your times. I think you should be able to plot against durations here, and will ultimately be happier.

Answer 1

[Askic V]

Why not trying straightforward:

function readVoltageDraw(a, startTime, ax)
   voltage = readVoltage(a, 'A1');
   t = datetime('now') - startTime;
   addpoints(h,datenum(t),voltage)
   ax.XLim = datenum([t-seconds(15) t]);
   datetick('x','keeplimits')
   drawnow
end

and call it just like this:

while (voltage > 2.9)
       writeDigitalPin(a,'D2',1);
       disp 'Pump is on!'
       readVoltageDraw(a, startTime, ax)
       ...

[Md Zarif Raiyan]

clear all; close all;
a = arduino('COM3', 'Uno');
disp 'Connection received!'
pause (3);
figure
h = animatedline;
ax = gca;
ax.YGrid = 'on';
ax.YLim = [2.4 3.8];
title('Moisture Sensor Voltage vs Time (live)');
xlabel('Time [HH:MM:SS]');
ylabel('Voltage [volt]');
stop = false;
startTime = datetime('now');
while ~stop
   readVoltageDraw(a, startTime, ax)
   while (voltage < 2.9)
       readVoltageDraw(a, startTime, ax)
   end
   while (voltage > 2.9)
       writeDigitalPin(a,'D2',1);
       disp 'Pump is on!'
       readVoltageDraw(a, startTime, ax)
       if (voltage < 2.9)
           writeDigitalPin(a,'D2',0)
           disp 'Pump is off!'
           while (voltage < 2.9)
               readVoltageDraw(a, startTime, ax)
           end
       end
   end
end

function readVoltageDraw(a, startTime, ax)
   voltage = readVoltage(a, 'A1');
   t = datetime('now') - startTime;
   addpoints(h,datenum(t),voltage)
   ax.XLim = datenum([t-seconds(15) t]);
   datetick('x','keeplimits')
   drawnow
end

I have rewritten the code as such. However I am receving this error message:

Unrecognized function or variable 'h'.

Error in MinorProjecthelp>readVoltageDraw (line 37)
   addpoints(h,datenum(t),voltage)

Error in MinorProjecthelp (line 16)
   readVoltageDraw(a, startTime, ax)

[Torsten]

If "h" is needed in "readVoltageDraw", you must pass it there as input argument...

[Md Zarif Raiyan]

Just did that, thank you, it works now :)

[Askic V]

Yes, I forgot to specify animated handle h as an input argument. Thank you Torsten for point that out.