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I am attempting to display in QGIS a numerical value taken from the attribute table of a particular scene and display it in the top right corner of the project layer.

So far I have been successful in being able to preview the value in the attribute table

aggregate('scene','array_agg',"gfs_speed_av") 

expression preview

However the value previewed does not show up in the title decorations.

I have also tried this expression below which just displays the expression as text

to_string(aggregate('scene','array_agg',"gfs_speed_av"))

see below

Why isn't my first expression displaying like shown in the preview tab?

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    What GIS software are you using?
    – PolyGeo
    Commented May 2, 2023 at 10:40
  • @PolyGeo QGIS . Commented May 2, 2023 at 11:28
  • Please Edit the question in response to requests for clarification.
    – Vince
    Commented May 2, 2023 at 11:29
  • Try to enclose your expression in an eval() function: eval ( [your expression] ).
    – Babel
    Commented May 2, 2023 at 12:27

1 Answer 1

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Your first expression creates an array, as you can see in the preview: [4.26]. To get the (first) value, use either:

If only the expression in string form is shown in the result, evaluate it (convert the string to functions) using function eval(): eval ( [your expression] ) to get the calculated outpug.

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