Clarify that x/y coordinates only work with the time scale (#4826)

diff --git a/docs/charts/bar.md b/docs/charts/bar.md
index 524c795214cccd018cabf9362459eae4433ea261..cd5e8c9f39137f54c03e051986e92e55277e5e73 100644 (file)
--- a/docs/charts/bar.md
+++ b/docs/charts/bar.md
@@ -152,7 +152,7 @@ The `data` property of a dataset for a bar chart is specified as a an array of n
 data: [20, 10]
 ```
 
-You can also specify the dataset as x/y coordinates.
+You can also specify the dataset as x/y coordinates when using the [time scale](./time.md).
 
 ```javascript
 data: [{x:'2016-12-25', y:20}, {x:'2016-12-26', y:10}]