diff --git a/_examples/scatter/main.go b/_examples/scatter/main.go
index de8ef3a..4347868 100644
--- a/_examples/scatter/main.go
+++ b/_examples/scatter/main.go
@@ -12,7 +12,7 @@ import (
 
 func drawChart(res http.ResponseWriter, req *http.Request) {
 
-	viridisByY := func(xr, yr chart.Range, x, y float64) drawing.Color {
+	viridisByY := func(xr, yr chart.Range, index int, x, y float64) drawing.Color {
 		return chart.Viridis(y, yr.GetMin(), yr.GetMax())
 	}
 
diff --git a/draw.go b/draw.go
index 3f06cde..3185086 100644
--- a/draw.go
+++ b/draw.go
@@ -66,11 +66,11 @@ func (d draw) LineSeries(r Renderer, canvasBox Box, xrange, yrange Range, style
 
 			dotWidth := defaultDotWidth
 			if style.DotWidthProvider != nil {
-				dotWidth = style.DotWidthProvider(xrange, yrange, vx, vy)
+				dotWidth = style.DotWidthProvider(xrange, yrange, i, vx, vy)
 			}
 
 			if style.DotColorProvider != nil {
-				dotColor := style.DotColorProvider(xrange, yrange, vx, vy)
+				dotColor := style.DotColorProvider(xrange, yrange, i, vx, vy)
 
 				r.SetFillColor(dotColor)
 				r.SetStrokeColor(dotColor)
diff --git a/value_provider.go b/value_provider.go
index 030e802..f6e7824 100644
--- a/value_provider.go
+++ b/value_provider.go
@@ -37,10 +37,10 @@ type FullBoundedValueProvider interface {
 }
 
 // SizeProvider is a provider for integer size.
-type SizeProvider func(xrange, yrange Range, x, y float64) float64
+type SizeProvider func(xrange, yrange Range, index int, x, y float64) float64
 
 // ColorProvider is a general provider for color ranges based on values.
 type ColorProvider func(v, vmin, vmax float64) drawing.Color
 
 // DotColorProvider is a provider for dot color.
-type DotColorProvider func(xrange, yrange Range, x, y float64) drawing.Color
+type DotColorProvider func(xrange, yrange Range, index int, x, y float64) drawing.Color