Question on Streaming Plot Data

Greetings, I will be streaming pressure transducer and TC values into Bokeh for real time plotting and data visualization every 100 ms. When plotting the stream data does Bokeh replot all the values every scan or does it keep on screen the old values and plot the new ones. The reason I ask is that our experiments can run for 2-3 hours and we would like to see how our experiment is progressing from the start to the current scan if you are replotting all the values than I can see how the process can be bogged down.

Thanks.

–Vivek

Hi,

ColumnDataSource has a .stream method for efficiently updating to "append-only" data sources, by only sending the new data, and not re-sending all the old data. It can be configured with a simple rollover threshold so that the data sources in the browser do not grow without bound:

  http://bokeh.pydata.org/en/latest/docs/reference/models/sources.html#bokeh.models.sources.ColumnDataSource.stream

For a concrete example to study, you can refer to the OHLC example:

  https://github.com/bokeh/bokeh/tree/master/examples/app/ohlc

If you need something more sophisticated than the simple "start discarding things after N number of data points" behavior in BokehJS, that's probably possible to, but would be a bit more involved.

Thanks,

Bryan

···

On Jan 13, 2017, at 10:10 AM, Vivek Dwivedi <[email protected]> wrote:

Greetings, I will be streaming pressure transducer and TC values into Bokeh for real time plotting and data visualization every 100 ms. When plotting the stream data does Bokeh replot all the values every scan or does it keep on screen the old values and plot the new ones. The reason I ask is that our experiments can run for 2-3 hours and we would like to see how our experiment is progressing from the start to the current scan if you are replotting all the values than I can see how the process can be bogged down.

Thanks.

--Vivek

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