[Qt-interest] Qt Charting Component - Feedback Request

[Sean Harmer]

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