diff --git a/readme.md b/readme.md
index 35e133e..9777b9b 100755
--- a/readme.md
+++ b/readme.md
@@ -55,6 +55,7 @@ API
 - *getHtmlLegend(colors, legend, callback);* : return a legend in html format
 - *getSortedlist();* : return the sorted serie in text format
 - *getClass();* : return a given value class
+- *getRangeNum()* : return the number/index of this.ranges that value falls into
 - *doCount();* : perform count feature by classes, used to display count feature in legend
  
  
@@ -68,4 +69,4 @@ Permission is hereby granted, free of charge, to any person obtaining a copy of
 The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- 
\ No newline at end of file
+