diff --git a/main.go b/main.go
index 98a57bc..8a950fc 100644
--- a/main.go
+++ b/main.go
@@ -138,6 +138,7 @@ func main() { // {{{
 	service.Register("/datapoint/update/{id}", false, false, actionDatapointUpdate)
 	service.Register("/datapoint/delete/{id}", false, false, actionDatapointDelete)
 	service.Register("/datapoint/values/{id}", false, false, pageDatapointValues)
+	service.Register("/datapoint/json/{id}", false, false, actionDatapointJson)
 
 	service.Register("/triggers", false, false, pageTriggers)
 	service.Register("/trigger/create/{sectionID}/{name}", false, false, actionTriggerCreate)
@@ -750,6 +751,37 @@ func pageDatapointValues(w http.ResponseWriter, r *http.Request, _ *session.T) {
 	page.Render(w, r)
 	return
 } // }}}
+func actionDatapointJson(w http.ResponseWriter, r *http.Request, _ *session.T) { // {{{
+	idStr := r.PathValue("id")
+	id, err := strconv.Atoi(idStr)
+	if err != nil {
+		httpError(w, werr.Wrap(err).Log())
+		return
+	}
+
+	fromStr := r.URL.Query().Get("f")
+	from, err := time.ParseInLocation("2006-01-02 15:04:05", fromStr[0:min(19, len(fromStr))], smonConfig.Timezone())
+	if err != nil {
+		httpError(w, werr.Wrap(err).Log())
+		return
+	}
+
+	toStr := r.URL.Query().Get("t")
+	to, err := time.ParseInLocation("2006-01-02 15:04:05", toStr[0:min(19, len(toStr))], smonConfig.Timezone())
+	if err != nil {
+		httpError(w, werr.Wrap(err).Log())
+		return
+	}
+
+	values, err := DatapointValues(id, from, to)
+	if err != nil {
+		httpError(w, werr.Wrap(err).Log())
+		return
+	}
+
+	j, _ := json.Marshal(values)
+	w.Write(j)
+} // }}}
 
 func pageTriggers(w http.ResponseWriter, r *http.Request, _ *session.T) { // {{{
 	areas, err := TriggersRetrieve()
diff --git a/sql/00021.sql b/sql/00021.sql
new file mode 100644
index 0000000..44b3afc
--- /dev/null
+++ b/sql/00021.sql
@@ -0,0 +1 @@
+CREATE INDEX datapoint_value_ts_idx ON public.datapoint_value (ts);
diff --git a/static/js/datapoint_values.js b/static/js/datapoint_values.js
new file mode 100644
index 0000000..3d6e80d
--- /dev/null
+++ b/static/js/datapoint_values.js
@@ -0,0 +1,73 @@
+function offsetTime(seconds) {
+	const el = document.getElementById('offset-time')
+	el.value = seconds
+	el.form.submit()
+}
+
+class Graph {
+	constructor(datapointID, initialData) {
+		this.dataset = new Dataset(datapointID, initialData)
+
+		this.createGraph()
+	}
+
+	async createGraph() {
+		this.graphValues = document.getElementById('graph-values');
+
+		const values = [{
+			x: this.dataset.xValues(),
+			y: this.dataset.yValues(),
+		}]
+
+		this.layout = {
+			margin: {
+				t: 24,
+				r: 0,
+			},
+		}
+
+		Plotly.react(this.graphValues, values, this.layout);
+		this.graphValues.on('plotly_relayout', attr => this.relayoutHandler(attr))
+	}
+
+	async relayoutHandler(attr) {
+		if (!attr.hasOwnProperty('xaxis.range[0]') || !attr.hasOwnProperty('xaxis.range[1]'))
+			return
+
+		this.dataset.extend(attr['xaxis.range[0]'], attr['xaxis.range[1]'])
+			.then(() => {
+				const values = [{
+					x: this.dataset.xValues(),
+					y: this.dataset.yValues(),
+				}]
+				Plotly.react(this.graphValues, values, this.layout)
+			})
+	}
+}
+
+class Dataset {
+	constructor(id, initialData) {
+		this.datapointID = id
+		this.values = {}
+		initialData.forEach(v=>this.values[v.ID] = v)
+	}
+
+	xValues() {
+		return Object.keys(this.values).map(dpID => this.values[dpID].Ts)
+	}
+
+	yValues() {
+		return Object.keys(this.values).map(dpID => this.values[dpID].ValueInt.Int64)
+	}
+
+	async extend(from, to) {
+		return fetch(`/datapoint/json/${this.datapointID}?f=${from}&t=${to}`)
+			.then(data => data.json())
+			.then(datapointValues => {
+				datapointValues.forEach(dp=>{
+					this.values[dp.ID] = dp
+				})
+				document.getElementById('num-values').innerText = Object.keys(this.values).length
+			})
+	}
+}
diff --git a/views/pages/datapoint_values.gotmpl b/views/pages/datapoint_values.gotmpl
index 8d49b7b..e645665 100644
--- a/views/pages/datapoint_values.gotmpl
+++ b/views/pages/datapoint_values.gotmpl
@@ -7,6 +7,7 @@
 	{{ block "page_label" . }}{{end}}
 
 	<form action="/datapoint/values/{{ .Data.Datapoint.ID }}" method="get">
+
 		{{ if eq .Data.Datapoint.Datatype "INT" }}
 		<div>
 			<input name="display" value="graph" type="radio" id="display-graph" {{ if $graph }} checked {{ end}}> <label for="display-graph">Graph</label>
@@ -17,6 +18,7 @@
 		<input name="f" type="datetime-local" step="1" value="{{ .Data.TimeFrom }}">
 		<input name="t" type="datetime-local" step="1" value="{{ .Data.TimeTo }}">
 		<button>OK</button>
+
 	</form>
 	<br><br>
 
@@ -24,22 +26,17 @@
 	<div class="graph">
 		<div id="graph-values"></div>
 	</div>
+
+	<div style="margin-top: 8px;">
+		<b>Number of values:</b>
+		<span id="num-values">{{ len .Data.Values }}</span>
+	</div>
 	<script type="text/javascript">
-		const graphValues = document.getElementById('graph-values');
-		let data = {{ .Data }}
-		let x = data.Values.map(d => d.Ts)
-		let y = data.Values.map(d => d.ValueInt.Int64)
-		Plotly.newPlot(
-			graphValues,
-			[
-				{
-					x,
-					y,
-				},
-			], {
-				margin: { t: 0 },
-			}
-		);
+		new Graph(
+			{{ .Data.Datapoint.ID }},
+			{{ .Data.Values }},
+		)
+
 	</script>
 	{{ else }}
 	<div id="values">
@@ -48,7 +45,7 @@
 		<div class="line"></div>
 		{{ range .Data.Values }}
 		<div class="value">{{ format_time .Ts }}</div>
-		<div class="value">{{ format_time .Value }}</div>
+		<div class="value">{{ .Value }}</div>
 		{{ end }}
 	</div>
 	{{ end }}