I have a trend in PI DataLink 2010 which traces two depth tags. These have positive values which increase downwards. I need to invert the trend's vertical scale (to show deeper values below shallower ones) but I don't see any option for it under Format (PI Trend Control Properties) or Change Scale.
Does anyone know if it can be done and, if not, whether this is supported in a later version of DataLink?
I did find that it will invert if I change the scale's min and max to absolute values with min > max, but then it seems to lose its gridlines, which is a show-stopper. (I also need it to be auto-ranged, but I thought I might have been able to achieve this by adding some code to calculate the range and writing the min/max values to the control's properties.)
My current workaround is to use a sampled data function with -'tagname' expressions to get negative depths into hidden columns on the worksheet, use this data as source of the trend's traces, and select (#,##0) for the vertical scale format to almost hide from the user that the values are negative. This is not ideal, but I could live with it if necessary.
Thanks for any advice.
Ian