Visualization

Report design in Power BI is mostly a decision about what to leave out. A page has room for roughly one question; a visual has room for roughly one comparison. Most reports that feel hard to read are not badly styled — they are answering four questions at once with six charts that each try to answer all of them.

The visual types guide is the place to start, followed by dashboard layout and then the interaction features: drill through, bookmarks, tooltips and slicers. Conditional formatting is worth learning properly rather than by trial and error, since it is the cheapest way to make a table readable without adding another visual to the page.

Two things are worth saying plainly. Colour should carry meaning or be absent; a report with eleven accent colours is not more informative than one with two. And charts are expensive at query time — a page of twenty visuals runs twenty queries, which is why a report that was fast with three can crawl with twenty.