Charts: Choosing, Building and Refining
Match the chart to the message
Column and bar charts compare discrete categories, line charts show trends over continuous time, pie charts show parts of one whole (one series only, few slices), scatter (XY) charts show correlation between two numeric variables, and combination charts plot a series on a secondary axis when its scale differs greatly. A common exam trap is a pie chart built from several series - it only plots the first, so the picture is misleading.
Know your ranges
A chart reads a data range split into series and categories. If the chart shows months as separate series and product names along the axis, use Switch Row/Column. Blank cells may plot as zero or as gaps depending on the 'Hidden and Empty Cells' setting. Charts do not expand automatically when rows are added outside the source range, so build from a formatted table or a dynamic named range, or edit the range reference.
Elements to label
Every well-formed chart has a chart title, axis titles with units, a legend where more than one series exists, and data labels when exact values matter. Format the value axis with minimum, maximum, major unit and number format especially when a truncated axis exaggerates differences. Use logarithmic scale only for orders of magnitude.
Placement and polish
Charts can be embedded in a worksheet or placed on their own chart sheet. Treat them as objects: move, resize, change type, add a trendline or sparkline, and set print settings so an embedded chart prints on one page.
Worked example
Sales in units and revenue in currency share the same categories but not the same scale. Plot both as a combo chart, revenue as a line on the secondary axis, so neither series is flattened against the axis.
Rule of thumb
Before formatting anything, ask what the reader should conclude in five seconds; if the chart type cannot deliver that sentence, change the type.