go-chart/sma_series.go
2018-12-06 16:38:58 +01:00

123 lines
2.8 KiB
Go

package chart
import (
"fmt"
util "git.gutmet.org/go-chart.git/util"
)
const (
// DefaultSimpleMovingAveragePeriod is the default number of values to average.
DefaultSimpleMovingAveragePeriod = 16
)
// Interface Assertions.
var (
_ Series = (*SMASeries)(nil)
_ FirstValuesProvider = (*SMASeries)(nil)
_ LastValuesProvider = (*SMASeries)(nil)
)
// SMASeries is a computed series.
type SMASeries struct {
Name string
Style Style
YAxis YAxisType
Period int
InnerSeries ValuesProvider
}
// GetName returns the name of the time series.
func (sma SMASeries) GetName() string {
return sma.Name
}
// GetStyle returns the line style.
func (sma SMASeries) GetStyle() Style {
return sma.Style
}
// GetYAxis returns which YAxis the series draws on.
func (sma SMASeries) GetYAxis() YAxisType {
return sma.YAxis
}
// Len returns the number of elements in the series.
func (sma SMASeries) Len() int {
return sma.InnerSeries.Len()
}
// GetPeriod returns the window size.
func (sma SMASeries) GetPeriod(defaults ...int) int {
if sma.Period == 0 {
if len(defaults) > 0 {
return defaults[0]
}
return DefaultSimpleMovingAveragePeriod
}
return sma.Period
}
// GetValues gets a value at a given index.
func (sma SMASeries) GetValues(index int) (x, y float64) {
if sma.InnerSeries == nil || sma.InnerSeries.Len() == 0 {
return
}
px, _ := sma.InnerSeries.GetValues(index)
x = px
y = sma.getAverage(index)
return
}
// GetFirstValues computes the first moving average value.
func (sma SMASeries) GetFirstValues() (x, y float64) {
if sma.InnerSeries == nil || sma.InnerSeries.Len() == 0 {
return
}
px, _ := sma.InnerSeries.GetValues(0)
x = px
y = sma.getAverage(0)
return
}
// GetLastValues computes the last moving average value but walking back window size samples,
// and recomputing the last moving average chunk.
func (sma SMASeries) GetLastValues() (x, y float64) {
if sma.InnerSeries == nil || sma.InnerSeries.Len() == 0 {
return
}
seriesLen := sma.InnerSeries.Len()
px, _ := sma.InnerSeries.GetValues(seriesLen - 1)
x = px
y = sma.getAverage(seriesLen - 1)
return
}
func (sma SMASeries) getAverage(index int) float64 {
period := sma.GetPeriod()
floor := util.Math.MaxInt(0, index-period)
var accum float64
var count float64
for x := index; x >= floor; x-- {
_, vy := sma.InnerSeries.GetValues(x)
accum += vy
count += 1.0
}
return accum / count
}
// Render renders the series.
func (sma SMASeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
style := sma.Style.InheritFrom(defaults)
Draw.LineSeries(r, canvasBox, xrange, yrange, style, sma)
}
// Validate validates the series.
func (sma SMASeries) Validate() error {
if sma.InnerSeries == nil {
return fmt.Errorf("sma series requires InnerSeries to be set")
}
return nil
}