X-Label unreadable in Line chart with large dataset.

[Kamstrup]

I downloaded the VPE 6 demo to see if we can use it in a project for a customer.
I am using the ActiveX component in Visual Dataflex 15.1.

The problem:
I am creating a line chart with > 50 000 datapoints. I'm setting the "ChartXLabelState" to "VCHART_LABEL_USER", then I use "ChartDataAddXLabel" to output an empty X-label, but for every 5000 datapoint, I use "ChartDataAddXLabel" with a real value (I would like only about 10 x-labels).

The X-labels are output, but are so small I have to zoom in (in PDF to about 3000%) to see the x-labels. The Y labels seems fine (most of the time).

I have tried the "ChartXLabelFontSizeFactor" (set it to 3.0), but it don't seem to make any difference.

Another problem is that when I output a chart with this many datapoints, VPE often chrashes when I try to resize the preview.

What seems to be missing, is the ability to set X-labels on just the datapoint you need (e.g. every 5000), and also be able to specify the font size of the X-label, as the automatic scaling don't seem to work with large datasets.

[IDEAL Software Support]

If you are using that many data points (50.000), you should ask yourself if this is really useful. Even on a 1.200 DPI printer this would require about 42 inches (106,68 cm) of paper-width in order to make each point printed as a single pixel (where such a pixel is 0.02 mm only).

I would recommend to use for example 5.000 points where each point is the median of 10 points. This reduces memory-usage drastically, and makes the drawing and handling of the chart object much faster, whilst not losing any visible information.

Setting an x-label to any empty string does not suppress that the label is drawn, so this does not help.

But we think your wish to have an x-step property for the labels (and also for the grid drawing) is important. We already implemented it this morning and it will be available with VPE v6.10, which will be released in a few weeks from now. The new properties are ChartXLabelStep and ChartXGridStep. If you acquire a license now, we are willing to provide you with a beta pre-release. In order to receive the beta version, please contact us by e-mail.

Regarding the crash: VPE may not crash. Therefore please send a sample file by e-mail, so we can see why it crashes.

[Kamstrup]

Thanks for this reply. Just what I needed:)
Regarding the 50000 datapoints, I totally agree with you, but our customer does not:) There could be spikes in the data, and for the customer this is what he is looking for.

Regarding the chrash, I have made a .VPE file, that crashes the VPE preview application when resizing. I'm guessing it's the same thing that happens to our application when resizing the preview. I will now start looking for an e-mail address to send it to.

Looking forward to testing the new x label steps in the new version (will be buying a license soon) .