Always use Don't summarize
Why no column bound to Ataytis Assurance should be summarised, how to recognise one that is, and how to fix it in the field well or once for every report.
Why a summarised column breaks a diagram
The visual needs your rows as they are: one row per node or connection. Power BI does not send a table exactly as it is stored. It sends one row for each combination of values in the columns that are not summarised, and works out each summarised column across the rows it combined.
While every row is different, a Sum changes nothing, so the problem stays hidden until rows repeat. Then a Health of 0.9 on two rows that match in every other column arrives as 1.8, and an Average arrives as a value no row holds. Nothing in what Power BI sends shows that this happened, so the visual cannot warn you.
Which wells summarise
| Well | Summarises |
|---|---|
| Data fields | Never. Every column here is used exactly as it is. |
| Values | Number columns, with Sum unless the column is set otherwise in the model. Any column here can also be switched to a summary such as Count or First. |
| Tooltips | The same as Values. |
Recognising a summarised column
In the well, a summarised field carries the summary in its name, such as Sum of Health, Average of Health, Count of Owner, First Owner or Earliest Last Verified. A field shown by its plain column name is not summarised.
Fixing it in the well
Open the field's menu
Select the arrow beside the field in Values or Tooltips.
Choose Don't summarize
The field goes back to its column name, such as Health instead of Sum of Health.
Changing a column's summarisation does not break its mapping.
Stopping it in every report
Select the column in the Data pane, and on the Column tools ribbon set Summarization to Don't summarize. Power BI then adds the column to any visual without summarising it, so Order, Health or a numeric identifier cannot be summed by accident.
Measures
A measure is a calculation, so it always summarises. Power BI works it out once for each row it sends to the visual, so write it to return the value for one node, such as the current health of one barrier.
When rows repeat on purpose
A table that stores each node once per month, site or scenario has rows that match in every bound column apart from their values. With Don't summarize those rows stay separate, and the visual reports that they disagree instead of adding them up, for example: A node is described by rows that disagree about Health, Status; the first row's values are shown. Put the column that separates the copies on a slicer, so the diagram shows one at a time.