How do I merge identical adjacent rows with dynamic row spans in Ag-Grid?

Most examples of rowspanning I have seen involve hard-coded values.

How would I create row-spans dynamically based on the column values? Specifically, I'd like to dynamically merge all adjacent identical rows into one cell, to get a result such as this:

Ag-Grid - Only Date rows are to be span

Can the function logic to define a row-span access the values from other rows? Can it do so relative to itself (e.g. next row, prev row)?

While defining your column definitions, you can specify the row span of each column.

For example this will specify 5 rows merged

colDef = {
    headerName: "Country",
    field: "country",
    rowSpan: 5
}

Also you can have it as a function to be more dynamic

colDef = {
    headerName: "Country",
    field: "country",
    rowSpan: function(params) {
        return params.data.country==='Russia' ? 2 : 1;
    }
}

This will specify 2 merged rows if the country is Russia and 1 for everything else. This is taken from AG-Grid documentation here.

I suggest reading more on the row span in the documentation. It explains it well.