Strange behavior with Time axis series

[logikdev]

Hello!

I am trying to display a chart containing a few time series and had initially got it to work by using simple incrementing integers for the X axis, which resulted in this:

Since i want to perform FFTs on these datasets, i needed to convert the X axis to be a time axis. I used the TimeAxis sample as a guide. This worked as expected for the FFT charts, but had an odd side effect as you can see here:

The following code block produces the initial result:

 dataSetPressureL.add(i, datapoint.pressureLValue); 
 dataSetPressureR.add(i, datapoint.pressureRValue); 
 dataSetSum.add(i, (datapoint.pressureLValue + datapoint.pressureRValue));
 dataSetW.add(i, review_powerHashMap.get(datapoint.now.getTime() / 1000));
 dataSetHR.add(i, review_heartrateHashMap.get(datapoint.now.getTime() / 1000));
 dataSetCad.add(i, review_cadenceHashMap.get(datapoint.now.getTime() / 1000));

While this code block produces the strange artefacts:

 dataSetPressureL.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, datapoint.pressureLValue); 
 dataSetPressureR.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, datapoint.pressureRValue);
 dataSetSum.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, (datapoint.pressureLValue + datapoint.pressureRValue));
 dataSetW.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, review_powerHashMap.get(datapoint.now.getTime() / 1000));
 dataSetHR.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, review_heartrateHashMap.get(datapoint.now.getTime() / 1000));
 dataSetCad.add((datapoint.now.getTime() + tz.getOffset(datapoint.now.getTime())) / 1000, review_cadenceHashMap.get(datapoint.now.getTime() / 1000));

I'm not quite sure how to attack this and would appreciate any suggestion or help anyone would provide. Thank you!

[wirew0rm]

Hey and welcome to chart-fx 👋

If your datapoint.now.getTime() function returns an integer, your division by 1000 will be performed as an integer division, so you will only get points at full seconds, which would explain how your plot is looking. Try to change this to / 1000.0 (or even better * 1e-3) and you should be good to go. If this is not the problem, please let me know so I can look into it.

[logikdev]

Hi!

Thanks for the code block edits and the prompt reply! Of course, as i was writing this post, it got my mind thinking about things a bit differently and checked the individual timestamps i was feeding to the datasets and you are 100% correct in your assessment.

I will implement your suggestions and go from there. Since this isn't strictly a Chartfx issue, is it worthwhile to leave this discussion up for others to find or should i remove it entirely?

[wirew0rm]

Glad that it works now :)
As this is a somewhat common mistake, I think others can also benefit from it, too.
I personally also like these questions, as they are our main way to see what people are doing with the library.
So no need to remove it from my POV.

[logikdev]

It's not fully functional yet but your help put me on the right path to address the calculations i was doing wrong in regards to integer/double precision so that's what i'm working on at the moment.

Thanks again for your help. This is a great project. I've very to have found it while researching for my own project. Cheers!