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I have a large dataset of multiple drill holes that have been tested. The sheet is an excel sheet and contains the holeID, depth, easting, northing and assay results.

example:

enter image description here

Is there a way I could get Qgis to display the highest down hole value for each drill hole?

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Here's one way. I have two layers, one is a plain table layer with no geometry that you can create from a sheet in a spreadsheet file. Its attribute table looks like this (I've copied your example but simplified the names):

enter image description here

Then I have a layer, points with matching ID in its attributes, which looks like this:

enter image description here

It has one feature per borehole ID. You should probably create this from your spreadsheet by getting a sheet with one row for each borehole with just the ID and coordinates in it. That way you then have a layer with one point per borehole, regardless of how many samples taken at each borehole.

The maxAU column is what you want to create. This I made by opening the layer's attribute table and adding a new attribute created by an expression - click the "abacus" button. The expression is:

 aggregate( 'data', 'max', "Au", "ID"=attribute(@parent, 'ID'))

This says that the value in the new column in points will come from the layer called data, and it will be the maximum value of the "Au" column in data, but only in the rows that match the "ID" value in data with the "ID" value in the "parent" feature, which is the feature in the points layer. The result is the maxAU column in the table above.

You can then use that value in QGIS' mapping engine to colour or scale points.

You'll have to repeat this by hand for all the different elements in your data, or find some way of automating it...

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  • Thank you! What I ended up doing was creating new columns for northing & easting in the assay table - and then set the symbology to graduated
    – Donny
    Feb 15, 2019 at 9:02

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