Clarification of fill property in Dataset Structure

docs/03-Line-Chart.md

@@ -38,7 +38,7 @@ data | See [data point](#line-chart-data-points) section | The data to plot in a
 label | `String` | The label for the dataset which appears in the legend and tooltips
 xAxisID | `String` | The ID of the x axis to plot this dataset on
 yAxisID | `String` | The ID of the y axis to plot this dataset on
-fill | `Boolean` | If true, fill the area under the line
+fill | `Boolean or String` | Allowed values: <br>`true` fill the area between 0 and the value<br>`false` do not fill the area<br>`bottom` fill the area from the bottom of the chart<br>`top` fill the area from the top of the chart
 cubicInterpolationMode | `String` | Algorithm used to interpolate a smooth curve from the discrete data points. Options are 'default' and 'monotone'. The 'default' algorithm uses a custom weighted cubic interpolation, which produces pleasant curves for all types of datasets. The 'monotone' algorithm is more suited to `y = f(x)` datasets : it preserves monotonicity (or piecewise monotonicity) of the dataset being interpolated, and ensures local extremums (if any) stay at input data points. If left untouched (`undefined`), the global `options.elements.line.cubicInterpolationMode` property is used.
 lineTension | `Number` | Bezier curve tension of the line. Set to 0 to draw straightlines. This option is ignored if monotone cubic interpolation is used. *Note* This was renamed from 'tension' but the old name still works.
 backgroundColor | `Color` | The fill color under the line. See [Colors](#chart-configuration-colors)
@@ -51,13 +51,13 @@ borderJoinStyle | `String` | Line joint style. See [MDN](https://developer.mozil
 pointBorderColor | `Color or Array<Color>` | The border color for points.
 pointBackgroundColor | `Color or Array<Color>` | The fill color for points
 pointBorderWidth | `Number or Array<Number>` | The width of the point border in pixels
-pointRadius | `Number or Array<Number>` | The radius of the point shape. If set to 0, nothing is rendered. 
+pointRadius | `Number or Array<Number>` | The radius of the point shape. If set to 0, nothing is rendered.
 pointHoverRadius | `Number or Array<Number>` | The radius of the point when hovered
 pointHitRadius | `Number or Array<Number>` | The pixel size of the non-displayed point that reacts to mouse events
 pointHoverBackgroundColor | `Color or Array<Color>` | Point background color when hovered
 pointHoverBorderColor | `Color or Array<Color>` | Point border color when hovered
 pointHoverBorderWidth | `Number or Array<Number>` | Border width of point when hovered
-pointStyle | `String, Array<String>, Image, Array<Image>` | The style of point. Options are 'circle', 'triangle', 'rect', 'rectRot', 'cross', 'crossRot', 'star', 'line', and 'dash'. If the option is an image, that image is drawn on the canvas using `drawImage`. 
+pointStyle | `String, Array<String>, Image, Array<Image>` | The style of point. Options are 'circle', 'triangle', 'rect', 'rectRot', 'cross', 'crossRot', 'star', 'line', and 'dash'. If the option is an image, that image is drawn on the canvas using `drawImage`.
 showLine | `Boolean` | If false, the line is not drawn for this dataset
 spanGaps | `Boolean` | If true, lines will be drawn between points with no or null data
 steppedLine | `Boolean` | If true, the line is shown as a stepped line and 'lineTension' will be ignored
@@ -146,7 +146,7 @@ These are the customisation options specific to Line charts. These options are m
 Name | Type | Default | Description
 --- | --- | --- | ---
 showLines | Boolean | true | If false, the lines between points are not drawn
-spanGaps | Boolean | false | If true, NaN data does not break the line 
+spanGaps | Boolean | false | If true, NaN data does not break the line
 
 You can override these for your `Chart` instance by passing a member `options` into the `Line` method.