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Speed up plotting to MSWindows graphics window

7 messages · Duncan Murdoch, Mike Marchywka, Uwe Ligges +2 more

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Hello,

I am working on a project analysing the performance of motor-vehicles 
through messages logged over a CAN bus.

I am using R 2.12 on Windows XP and 7

I am currently plotting the data in R, overlaying 5 or more plots of 
data, logged at 1kHz, (using plot.ts() and par(new = TRUE)).
The aim is to be able to pan, zoom in and out and get values from the 
plotted graph using a custom Qt interface that is used as a front end to 
R.exe (all this works).
The plot is drawn by R directly to the windows graphic device.

The data is imported from a .csv file (typically around 100MB) to a matrix.
(timestamp, message ID, byte0, byte1, ..., byte7)
I then separate this matrix into several by message ID (dimensions are 
in the order of 8cols, 10^6 rows)

The panning is done by redrawing the plots, shifted by a small amount. 
So as to view a window of data from a second to a minute long that can 
travel the length of the logged data.

My problem is that, the redrawing of the plots whilst panning is too 
slow when dealing with this much data.
i.e.: I can see the last graphs being drawn to the screen in the 
half-second following the view change.
I need a fluid change from one view to the next.

My question is this:
Are there ways to speed up the plotting on the MSWindows display?
By reducing plotted point densities to *sensible* values?
Using something other than plot.ts() - is the lattice package faster?
I don't need publication quality plots, they can be rougher...

I have tried:
-Using matrices instead of dataframes - (works for calculations but not 
enough for plots)
-increasing the max usable memory (max-mem-size) - (no change)
-increasing the size of the pointer protection stack (max-ppsize) - (no 
change)
-deleting the unnecessary leftover matrices - (no change)
-I can't use lines() instead of plot() because of the very  different 
scales (rpm-10000, flags -1to3)

I am going to do some resampling of the logged data to reduce the vector 
sizes.
(removal of *less* important data and use of window.ts())

But I am currently running out of ideas...
So if sombody could point out something, I would be greatfull.

Thanks,

Jonathan Gabris
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Jonathan Gabris wrote:
I don't think there are any ways to plot in the standard device that are 
significantly faster than what you are doing if you want to see the 
updates.  (I think it would be substantially faster if you hid the 
graphics window during the updates, but that won't suit you.)

I'd suggest plotting a subset of the data during the updates, then plot 
the full dataset when it stops moving.  For example, only plot a few 
hundred points, even spaced through the time series.

Duncan Murdoch
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Well, hard to know but it would help to know where all the time is going.
Usually people start complaining when VM thrashing is common but if you are
CPU limited you could try restricting the range of data you want to plot
rather than relying on the plot to just clip the largely irrelevant points
when you are zoomed in. It should not be too expensive to find the
limits either incrementally or with binary search on ordered time series. 
Presumably subsetting is fast using? foo[a:b,] 

One thing you may want to try for change of scale is wavelet? or
multi-resolution analysis. You can make a tree ( increasing memory usage
but even VM here may not be a big penalty if coherence is high ) and
display the resolution appropriate for the current scale.
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On 27.04.2011 12:56, Duncan Murdoch wrote:
... and it highly depends on the data what can be improved. Example: For 
signals essential consisting of sine functions (i.e. harmonic signals), 
I am using a little dirty trick in the tuneR package, but that makes the 
assumption of having a high frequency sample of a harmonic signal 
without too much noise.

Uwe Ligges
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----------------------------------------
well, maybe time series knows the data to be ordered, I never use
that, but in general it has to go check each point and clip the out
of range ones. It could I suppose binary search for start/end points
but I don't know.Based on what you said it sounds like it does not.
1 day later
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If you are plotting that many data points, you  might want to look at
'hexbin' as a way of aggregating the values to a different
presentation.  It is especially nice if you are doing a scatter plot
with a lot of data points and trying to make sense out of it.
On Wed, Apr 27, 2011 at 5:16 AM, Jonathan Gabris <jonathan at k-m-p.nl> wrote: