Sparkline Dynamic Tag History Expression Binding


I would like to use a sparkline display along with my transmitter value in Perspective. My goal is to provide a tag path to the view that contains the transmitter and sparkline to make them interactive. The transmitter parameter passing works fine, but I cannot get the sparkline to work properly.

According to this video, it should be possible to create a custom array of objects, with each object containing values for path, alias, and aggregate and use it in a Tag History Binding. The video is for a table but I think it should work for a sparkline as well since they both use Tag History Binding—expression/8.0

I followed the format in the manual.;

"Using Dynamic Tag Paths

Tag History bindings have the option to list out Tag paths, or to use an expression to build a Tag path. It is common to create a dynamic path or set of paths as a component property, that you then reference in other places. You can use as many Tag paths as you want, but they must all follow this format:

key [array] 

    [0] {object}
        aggregate value
        alias value
        path value
        aggregate value
        alias value
        path value


Here is my CUSTOM property for the sparkline:

When I bind the Tag History directly to a tag, it works fine, but when I try to use an expression, I get an error message:

What am I doing wrong here? The PV is the data source for both the transmitter and sparkline. I know the sparkline uses tag history whereas the transmitter uses direct or indirect tags, but making the sparkline dynamic should be as simple as making the transmitter dynamic.

I can make the tag binding dynamic by using a parameter. All this does is to alter the tag path by adding some text to it.

Why can’t the same option be used in a Tag History Binding? I understand a dataset is required, but if the configuration can take a direct tag path and create the dataset behind the scene, why can’t it use a parameter to alter the tag path and do the same thing as a direct path?

Thank you,

I don’t think it accepts default as an aggregate. Try something explicit, like average.