getpoints function is not saving variables outside of loop

Question

Gabrielle Mills 2018-4-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394753-getpoints-function-is-not-saving-variables-outside-of-loop

评论： Madhu Govindarajan 2018-4-26

I am attempting to edit an existing code that will read ECG data from an Arduino Uno (in COM3), display the live ECG on a plot, and save the recorded data points. I am able to read the data and display it live, but the variables with the ECG data and time points do not save outside of the "for" loop. I think this may be an issue with the getpoints function, but any advice or input on how to save the variables ECGLogs and timeLogs would be greatly appreciated!

Here's the code I have:

 ECG = arduino('COM3');
%%Acquire and display live data
figure
h = animatedline;
ax = gca;
ax.YGrid = 'on';
ax.YLim = [0 2];
startTime = datetime('now');
for i= 1:500
  % Read current voltage value
  v = readVoltage(ECG,'A0');
  [timeLogs,ECGLogs] = getpoints(h); 
  f = [timeLogs,ECGLogs];
  % Get current time
  t =  datetime('now') - startTime;
  % Add points to animation
  addpoints(h,datenum(t),v);
  % Update axes
  ax.XLim = datenum([t-seconds(15) t]);
  datetick('x','keeplimits')
  drawnow
  % Check stop condition
  stop = readDigitalPin(ECG,'D12');
  i = i+1;
end

2 个评论
显示无隐藏无

David Fletcher 2018-4-13

Effectively on each iteration of the loop you are throwing away the previous values of timeLogs and ECGlogs by overwriting f with an array of the new values. What is the size of of timelogs and ECGlogs - are they scaler values?

Gabrielle Mills 2018-4-15

在 MATLAB Online 中打开

When I stop the program, they become 0x0 double vectors. However, when the program is running and I do not suppress the output, I get printed values like these:

timeLogs =
   1.0e-04 *
Columns 1 through 10
    0.0318    0.0692    0.0769    0.0834    0.0917    0.1020    0.1065    0.1124    0.1179    0.1251
Columns 11 through 20
    0.1294    0.1362    0.1404    0.1446    0.1490    0.1531    0.1575    0.1622    0.1664    0.1713
Columns 21 through 30
    0.1759    0.1800    0.1844    0.1911    0.1954    0.2007    0.2062    0.2110    0.2157    0.2206
Columns 31 through 40
    0.2256    0.2299    0.2341    0.2392    0.2443    0.2494    0.2542    0.2584    0.2626    0.2668
Columns 41 through 46
    0.2714    0.2765    0.2817    0.2863    0.2917    0.2969
 ECGLogs =
Columns 1 through 10
    1.1584    1.1584    1.1584    1.1584    1.1535    1.1535    1.1535    1.1535    1.1535    1.1535
Columns 11 through 20
    1.1535    1.1486    1.1486    1.1486    1.1486    1.1486    1.1486    1.1486    1.1437    1.1437
Columns 21 through 30
    1.1437    1.1437    1.1437    1.1437    1.1437    1.1437    1.1437    1.1388    1.1437    1.1388
Columns 31 through 40
    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388
Columns 41 through 46
    1.1388    1.1388    1.1388    1.1388    1.1388    1.1388

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Madhu Govindarajan 2018-4-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394753-getpoints-function-is-not-saving-variables-outside-of-loop#answer_315639

Once you have ran the for loop, without closing the figure try running the following command outside of the for loop.

[timeLogs,ECGLogs] = getpoints(h);

This should give you the datapoints from the animatedline.

Also inside the for loop, you don't need i = i+1;

4 个评论
显示 2更早的评论隐藏 2更早的评论

Gabrielle Mills 2018-4-18

I just copied and pasted your code (and adjusted the v value as necessary), and I am still having the same issue. What version of MATLAB are you running? Because that is the only factor I can think of that may change the way the program is running.

Madhu Govindarajan 2018-4-26