[SPARK-10669] [DOCS] Link to each language's API in codetabs in ML docs: spark.mllib

In the Markdown docs for the spark.mllib Programming Guide, we have code examples with codetabs for each language. We should link to each language's API docs within the corresponding codetab, but we are inconsistent about this. For an example of what we want to do, see the "ChiSqSelector" section in https://github.com/apache/spark/blob/64743870f23bffb8d96dcc8a0181c1452782a151/docs/mllib-feature-extraction.md
This JIRA is just for spark.mllib, not spark.ml.

Please let me know if more work is needed, thanks a lot.

Author: Xin Ren <iamshrek@126.com>

Closes #8977 from keypointt/SPARK-10669.

1 files changed, 4 insertions, 0 deletions

diff --git a/docs/mllib-optimization.md b/docs/mllib-optimization.md
index 6cabc1610a..a3bd130ba0 100644
--- a/docs/mllib-optimization.md
+++ b/docs/mllib-optimization.md
@@ -218,6 +218,8 @@ L-BFGS optimizer.
 <div class="codetabs">
 
 <div data-lang="scala" markdown="1">
+Refer to the [`LBFGS` Scala docs](api/scala/index.html#org.apache.spark.mllib.optimization.LBFGS) and [`SquaredL2Updater` Scala docs](api/scala/index.html#org.apache.spark.mllib.optimization.SquaredL2Updater) for details on the API.
+
 {% highlight scala %}
 import org.apache.spark.SparkContext
 import org.apache.spark.mllib.evaluation.BinaryClassificationMetrics
@@ -278,6 +280,8 @@ println("Area under ROC = " + auROC)
 </div>
 
 <div data-lang="java" markdown="1">
+Refer to the [`LBFGS` Java docs](api/java/org/apache/spark/mllib/optimization/LBFGS.html) and [`SquaredL2Updater` Java docs](api/java/org/apache/spark/mllib/optimization/SquaredL2Updater.html) for details on the API.
+
 {% highlight java %}
 import java.util.Arrays;
 import java.util.Random;