[Qt-interest] Qt Charting Component - Feedback Request

[Markus Franke]

Dear Syam,

well, actually I am receiving the points one by one with an interval of 
around 100ms.and I want to plot them with the same frequency like on an 
oscilloscope.

Best regards,
Markus Franke



qt-interest-bounces+franke.m=sebakmt.com at qt.nokia.com schrieb am 
07.03.2011 14:42:11:

> Hi,
> 
> On Monday 07 March 2011 10:04:39 Markus Franke wrote:
> > Dear all,
> > 
> > Syam Krishnan wrote:
> > > I'm very much interested in a good charting component. We've been 
trying
> > > 
> > > out Qwt, but it seems to have some performance problems when used 
with
> > > larger changing datasets.
> > > Our requirement often is plotting of continuous data. i.e. a new 
data
> > > point is available every 100 or 200 ms. Adding these points to the 
plot
> > > should be as light-weight an operation as possible. As far as I can 
see,
> > > 
> > > the current Qwt implementation requires copying the entire point 
list
> > > again and re-plotting from the beginning. This consumes a lot of 
CPU.
> > > I'd love to see an implementation where incremental plotting is
> > 
> > super-fast.
> > 
> > same with us. We're looking for a charting class which is able to
> > efficiently plot data which continously changes over time. Cycle times 
are
> > also around 50 to 100 milliseconds. Right now we do everything by
> > ourselves based on QWidget. However for a graph like a sinus wave 
which
> > amplitude continuously changes over time it's always needed to repaint 
the
> > whole waveform once a new data point is appended to the end. The whole
> > graphic needs to be shifted to the left as we only print the values of 
the
> > last few seconds.
> > 
> > Is there a way to efficiently plot this kind of data with your 
charting
> > class?
> 
> I have not tried it with data updates of this frequency yet however it 
is on 
> my list of things to do. I will test it using a worker thread to 
generate the 
> data.
> 
> In your use case, do you receive the new points one at a time or are 
they 
> batched together? How many points do you typically wish to plot at any 
one 
> time in such a plot?
> 
> I will take your numbers to test this out and get back to you.
> 
> Many thanks,
> 
> Sean
> 
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