Love Plotting has Inconsistent Plot Generation Times

[PlanetaryTyler]

Hello,

I've been trying to use gnuplot-iostream for live plotting Arduino data as it is read using my c++ program. I'm finding that it produces some unknown errors and the time it takes to plot can be very inconsistent.

Currently my code looks like this:

std::vector<std::vector<float>> data;
Gnuplot gp;
While (true)
{
/*
Bunch of code here to fill data variable with Arduino measurements 
over the last ~5 seconds with 200ms cadence, col 1 is times, col 2 is the data. 
There are more cols but I'm ignoring them for now
*/
gp << "plot '-' using 1:2 with points notitle\n"
gp.send1d(data)
}

This gives me errors such as

Gnuplot> 0
         ^ line 110: invalid command

I've tried a number of things, and the only thing that gets this invalid command error to go away is by having three \n at the end of the plot command.

In any of these cases the plotting command will either be instant or take up to a full second and is seemingly random.

Could you provide an example for having an updating plot that either gets rid of this errors or normalizes the plotting speed, or both? Ideally it would not use the pause command as that also interrupts the reading of data from the arduinos.

Thanks

[dstahlke]

The way you have it should be fine. I'm not sure what the problem is.  Note that both commands and data are sent in the same stream, so if it gets out of sync for some reason it can start interpreting data as if it were commands.  That is why you are getting that invalid command error.  But I'm not sure why. Take a look at example-misc.cc in the source code, function demo_animation().  It's basically what you wrote but sending data as binary rather than text (not that it should really matter). This demo is disabled for Windows because it tends to grab keyboard control and makes it hard to quit.  But you can read the comment inside the "#ifdef _WIN32" and remove that check. You may have better luck sending the data via a file rather than via the command stream.  Take a look at demo_tmpfile() also in example-misc.cc.  This example is not an animation, but you can easily turn it into one by plotting in a loop.  You will have to occasionally call clearTmpfiles() or these files will accumulate on disk.  If you pass a second parameter (which should be a filename) to the file1d call, it will use that named file rather than a temporary file. - Dan

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On 3/28/22 4:59 PM, PlanetaryTyler wrote: Hello, I've been trying to use gnuplot-iostream for live plotting Arduino data as it is read using my c++ program. I'm finding that it produces some unknown errors and the time it takes to plot can be very inconsistent. Currently my code looks like this: |std::vector<std::vector<float>> data; Gnuplot gp; While (true) { /* Bunch of code here to fill data variable with Arduino measurements over the last ~5 seconds with 200ms cadence, col 1 is times, col 2 is the data. There are more cols but I'm ignoring them for now */ gp << "plot '-' using 1:2 with points notitle\n" gp.send1d(data) } | This gives me errors such as |Gnuplot> 0 ^ line 110: invalid command | I've tried a number of things, and the only thing that gets this invalid command error to go away is by having three \n at the end of the plot command. In any of these cases the plotting command will either be instant or take up to a full second and is seemingly random. Could you provide an example for having an updating plot that either gets rid of this errors or normalizes the plotting speed, or both? Ideally it would not use the pause command as that also interrupts the reading of data from the arduinos. Thanks — Reply to this email directly, view it on GitHub <#23>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACMO4ELS7CHLBOAHT4TGYDVCJBXBANCNFSM5R4WSR2A>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>