const (
// ChartStackNone draws every series from the baseline, overlapping.
ChartStackNone ChartStack = iota
// ChartStackStacked piles each series on the ones before it. A missing value
// counts as zero.
ChartStackStacked
// ChartStackExpand stacks and normalizes every X to 100%, so the value axis
// runs from 0 to 1.
ChartStackExpand
)Type ChartStack
type ChartStack uint8ChartStack selects how series combine at one X.