"upside down" log chart

This seems to have been down to timing of bindings. Although the VM assigns YAxisRange (bound to the Y-axis VisibleRange property), I found I had to assign a dummy range to YAxisRange in the VM constructor. This now appears to have fixed the problem.

Hi Andrew,

Thanks for your inquiry.
We would appreciate if you provide us with more details regarding the issue you are experiencing, such as some pictures or mockups showing the current chart appearance compared to the desired state.

Please also share the steps to reproduce the described behavior in one of our examples from the WPF Examples suite, e.g. “Logarithmic Axis” example:
WPF Chart Logarithmic Axis Example – SciChart

I have also noticed you use an outdated SciChart version.
We recommend using the latest one, which is SciChart v8.6 currently, as it always includes all the latest fixes and updates.

Kind regards,
Lex,
SciChart technical support engineer

Hi, as explained in my question it’s a FastColumnRenderableSeries with logarithmic Y axis, and the values being plotted are small (1e-13 to 1e-7). The issue occurs because such small values convert to -ve numbers on a log axis, resulting in that strange upside down effect. It’s a “known” problem in that all charts do it, even in Excel.
I’ve attached an example screenshot showing the problem, where you can see the columns coming down from the top of the chart creating that “inverted” effect. (Ignore the pale blue area – that’s a box annotation).

I actually found a fix last night. As hinted at in my question, the answer was to use the ZeroLineY= attribute on the series, and set this to Y-axis min (1e-13). The crucial part is that I have to use a FastMountainRenderableSeries. ZeroLineY has no effect when using a column series, so I suspect that’s a bug (at least in my version of SciChart).
The second screenshot shows the chart rendered correctly with a mountain series.

Incidentally I’ve noticed a few strange issues over the years with FastColumnRenderableSeries. My chart lets users switch between a numeric and log Y-axis using your SwitchAxisTypeBehaviour (https://www.scichart.com/example/wpf-chart/wpf-chart-example-switch-axis-type-at-runtime/). When using a FastColumnRenderableSeries, the series often won’t render at all, but it all works faultlessly when using a mountain series instead.

This is a really strange one. The mountain series worked a couple of times then running the app later in the day it was back to being “inverted” (and no code changes in between). I’ve since noticed that the column series does actually work, but again only very occasionally. It’s as though the vast majority of the time the chart is ignoring the ZeroLineY setting. Here’s the xaml – as you can see it’s nothing out of the ordinary:

<s:SciChartSurface RenderOptions.EdgeMode="Aliased"
               DebugWhyDoesntSciChartRender="False"
               Margin="8">
<s:SciChartSurface.RenderableSeries>
    <s:FastMountainRenderableSeries DataSeries="{Binding ChartSeries}"
                                  ZeroLineY="1e-13"
                                  Fill="{Binding CollectorColour, Converter={StaticResource colorToBrushConv}}"
                                  Stroke="{Binding CollectorColour}"
                                  StrokeThickness="1"
                                  AntiAliasing="False" />
</s:SciChartSurface.RenderableSeries>
<s:SciChartSurface.XAxis>
    <s:NumericAxis Style="{StaticResource AxisStyle}"
                   s:RolloverModifier.AxisLabelTemplate="{StaticResource RolloverAxisLabelTemplate}"
                   AutoRange="Always"
                   DrawMajorGridLines="True"
                   MaxAutoTicks="8"
                   DrawLabels="True" />
</s:SciChartSurface.XAxis>
<s:SciChartSurface.YAxis>
    <s:LogarithmicNumericAxis x:Name="yAxisLog"
                              Style="{StaticResource AxisStyle}"
                              AutoRange="Never"
                              VisibleRange="{Binding YAxisRange, Mode=TwoWay}"
                              TextFormatting="0.0###e+00"
                              DrawMajorGridLines="True"
                              MaxAutoTicks="8"
                              DrawLabels="True"
                              AxisAlignment="Left" />
</s:SciChartSurface.YAxis>
<s:SciChartSurface.ChartModifier>
    <s:ModifierGroup>
        <s:RolloverModifier DrawVerticalLine="True"
                            ShowAxisLabels="True"
                            ShowTooltipOn="Always"
                            UseInterpolation="False"
                            SourceMode="AllVisibleSeries" />
    </s:ModifierGroup>
</s:SciChartSurface.ChartModifier>

I don’t suppose there’s any way to confirm whether this was a bug in v6.6 that has since been fixed?