diff --git a/cwidgets/expanded/cpu.go b/cwidgets/expanded/cpu.go
index 12cb775..a5c1491 100644
--- a/cwidgets/expanded/cpu.go
+++ b/cwidgets/expanded/cpu.go
@@ -16,8 +16,8 @@ func NewExpandedCpu() *ExpandedCpu {
 	cpu.Width = 50
 	cpu.X = 0
 	cpu.Y = 4
-	cpu.Data = cpu.hist.data
-	cpu.DataLabels = cpu.hist.labels
+	cpu.Data = cpu.hist.Data
+	cpu.DataLabels = cpu.hist.Labels
 	cpu.AxesColor = ui.ColorDefault
 	cpu.LineColor = ui.ColorGreen
 	return cpu
diff --git a/cwidgets/expanded/hist.go b/cwidgets/expanded/hist.go
index 1483149..b431f2e 100644
--- a/cwidgets/expanded/hist.go
+++ b/cwidgets/expanded/hist.go
@@ -1,74 +1,60 @@
 package expanded
 
 type IntHist struct {
-	data   []int
-	labels []string
+	Val    int   // most current data point
+	Data   []int // historical data points
+	Labels []string
 }
 
-func NewIntHist(max int) IntHist {
-	return IntHist{
-		data:   make([]int, max),
-		labels: make([]string, max),
+func NewIntHist(max int) *IntHist {
+	return &IntHist{
+		Data:   make([]int, max),
+		Labels: make([]string, max),
 	}
 }
 
-func (h IntHist) Append(val int) {
-	if len(h.data) == cap(h.data) {
-		h.data = append(h.data[:0], h.data[1:]...)
+func (h *IntHist) Append(val int) {
+	if len(h.Data) == cap(h.Data) {
+		h.Data = append(h.Data[:0], h.Data[1:]...)
 	}
+	h.Val = val
+	h.Data = append(h.Data, val)
+}
 
-	h.data = append(h.data, val)
+type DiffHist struct {
+	*IntHist
+	lastVal int
+}
+
+func NewDiffHist(max int) *DiffHist {
+	return &DiffHist{NewIntHist(max), -1}
+}
+
+func (h *DiffHist) Append(val int) {
+	if h.lastVal >= 0 { // skip append if this is the initial update
+		diff := val - h.lastVal
+		h.IntHist.Append(diff)
+	}
+	h.lastVal = val
 }
 
 type FloatHist struct {
-	data   []float64
-	labels []string
+	Val    float64   // most current data point
+	Data   []float64 // historical data points
+	Labels []string
 }
 
 func NewFloatHist(max int) FloatHist {
 	return FloatHist{
-		data:   make([]float64, max),
-		labels: make([]string, max),
+		Data:   make([]float64, max),
+		Labels: make([]string, max),
 	}
 }
 
 func (h FloatHist) Append(val float64) {
-	if len(h.data) == cap(h.data) {
-		h.data = append(h.data[:0], h.data[1:]...)
+	if len(h.Data) == cap(h.Data) {
+		h.Data = append(h.Data[:0], h.Data[1:]...)
 	}
-	h.data = append(h.data, val)
-}
-
-type DiffHist struct {
-	data    []int // data point derivatives
-	srcData []int // principal input data
-	labels  []string
-}
-
-func NewDiffHist(max int) DiffHist {
-	return DiffHist{
-		data:    make([]int, max),
-		srcData: make([]int, max),
-		labels:  make([]string, max),
-	}
-}
-
-// return most recent value
-func (h DiffHist) Last() int {
-	return h.data[len(h.data)-1]
-}
-
-func (h DiffHist) Append(val int) {
-	if len(h.data) == cap(h.data) {
-		h.data = append(h.data[:0], h.data[1:]...)
-	}
-	if len(h.srcData) == cap(h.srcData) {
-		h.srcData = append(h.srcData[:0], h.srcData[1:]...)
-	}
-
-	diff := val - h.srcData[len(h.srcData)-1]
-	if diff != val { // skip adding to data if this is the initial update
-		h.data = append(h.data, diff)
-	}
-	h.srcData = append(h.srcData, val)
+	h.Val = val
+	h.Data = append(h.Data, val)
 }
diff --git a/cwidgets/expanded/mem.go b/cwidgets/expanded/mem.go
index 49dc776..3b2a755 100644
--- a/cwidgets/expanded/mem.go
+++ b/cwidgets/expanded/mem.go
@@ -7,7 +7,7 @@ import (
 
 type ExpandedMem struct {
 	*ui.BarChart
-	hist IntHist
+	hist *IntHist
 }
 
 func NewExpandedMem() *ExpandedMem {
@@ -23,9 +23,9 @@ func NewExpandedMem() *ExpandedMem {
 	mem.X = 0
 	mem.Y = 14
 	mem.TextColor = ui.ColorDefault
-	mem.Data = mem.hist.data
+	mem.Data = mem.hist.Data
 	mem.BarColor = ui.ColorGreen
-	mem.DataLabels = mem.hist.labels
+	mem.DataLabels = mem.hist.Labels
 	mem.NumFmt = cwidgets.ByteFormatInt
 	return mem
 }
diff --git a/cwidgets/expanded/net.go b/cwidgets/expanded/net.go
index dddc7be..7213e0b 100644
--- a/cwidgets/expanded/net.go
+++ b/cwidgets/expanded/net.go
@@ -10,8 +10,8 @@ import (
 
 type ExpandedNet struct {
 	*ui.Sparklines
-	rxHist DiffHist
-	txHist DiffHist
+	rxHist *DiffHist
+	txHist *DiffHist
 }
 
 func NewExpandedNet() *ExpandedNet {
@@ -25,14 +25,14 @@ func NewExpandedNet() *ExpandedNet {
 	rx := ui.NewSparkline()
 	rx.Title = "RX"
 	rx.Height = 1
-	rx.Data = net.rxHist.data
+	rx.Data = net.rxHist.Data
 	rx.TitleColor = ui.ColorDefault
 	rx.LineColor = ui.ColorGreen
 
 	tx := ui.NewSparkline()
 	tx.Title = "TX"
 	tx.Height = 1
-	tx.Data = net.txHist.data
+	tx.Data = net.txHist.Data
 	tx.TitleColor = ui.ColorDefault
 	tx.LineColor = ui.ColorYellow
 
@@ -44,10 +44,10 @@ func (w *ExpandedNet) Update(rx int64, tx int64) {
 	var rate string
 
 	w.rxHist.Append(int(rx))
-	rate = strings.ToLower(cwidgets.ByteFormatInt(w.rxHist.Last()))
+	rate = strings.ToLower(cwidgets.ByteFormatInt(w.rxHist.Val))
 	w.Lines[0].Title = fmt.Sprintf("RX [%s/s]", rate)
 
 	w.txHist.Append(int(tx))
-	rate = strings.ToLower(cwidgets.ByteFormatInt(w.txHist.Last()))
+	rate = strings.ToLower(cwidgets.ByteFormatInt(w.txHist.Val))
 	w.Lines[1].Title = fmt.Sprintf("TX [%s/s]", rate)
 }