diff --git a/README.md b/README.md
index 1351d3c..6c639d1 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,27 @@ PHP project to generate cached SVG price charts
 Extract the files from https://github.com/seigler/Dash-SVG-chart/archive/master.zip where you want to use the chart, or from the command line run `git clone "https://github.com/seigler/Dash-SVG-chart" .` in the folder where you want the charts served from.
 
 ## Usage
-`<img src="path to the folder where you cloned this project">`
+In your PHP file:
+
+```php
+Header('Content-type: image/svg+xml; charset=utf-8');
+Header('Content-Disposition: inline; filename="Dash-24h-chart-' . date('Y-m-d\THisT') . '.svg"');
+include 'buffer.php';
+include 'SVGChartBuilder.php';
+
+/* your code here to generate $chartData */
+
+print SVGChartBuilder::renderStockChart($chartData, [
+  'width'=>800,
+  'height'=>250,
+  'lineColor'=>"#1C75BC",
+  'labelColor'=>"#777",
+  'smoothed'=>false
+]);
+```
+
+In your HTML:
+`<img src="path to the PHP file">`
 
 ## Credits
 
diff --git a/SVGChartBuilder.php b/SVGChartBuilder.php
index 47a1855..7f3dc5c 100644
--- a/SVGChartBuilder.php
+++ b/SVGChartBuilder.php
@@ -88,7 +88,7 @@ class SVGChartBuilder {
     http://vis4.net/blog/posts/doing-the-line-charts-right/
     */
     $aspectRatio = max(0.25, min(0.75, 1 / $averageAbsSlope));
-    $height = floor($aspectRatio * $width);
+    $height = $height ?? floor($aspectRatio * $width);
 
     function labelFormat($float, $places, $minPlaces = 0) {
       $value = number_format($float, max($minPlaces, $places));
diff --git a/index.php b/index.php
index 874357b..296606f 100644
--- a/index.php
+++ b/index.php
@@ -25,4 +25,10 @@ foreach ($last24h as $item) {
   $chartData[$item->date] = $item->weightedAverage;
 }
 
-print SVGChartBuilder::renderStockChart($chartData, 700, "#1C75BC");
+print SVGChartBuilder::renderStockChart($chartData, [
+  'width'=>800,
+  'height'=>250,
+  'lineColor'=>"#1C75BC",
+  'labelColor'=>"#777",
+  'smoothed'=>false
+]);