sparkchart.go
func (b *SparkChart) AddData(val float64) {
	b.mtx.Lock()
	defer b.mtx.Unlock()

	b.data = append(b.data, val)

	_, width := b.calculateBarArea()
	if len(b.data) > width {
		b.data = b.data[len(b.data)-width:]
	}
}
func (b *SparkChart) AddData(val float64) {
	b.mtx.Lock()
	defer b.mtx.Unlock()

	b.data = append(b.data, val)

	_, width := b.calculateBarArea()
	if len(b.data) > width {
		b.data = b.data[len(b.data)-width:]
	}
}
// AddData appends a new bar to a chart