Initial work fixing bug that was made clear in pr

Author: dittmarg

mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala

@@ -724,11 +724,12 @@ class SparseVector(
     if (size == 0) {
       -1
     } else {
-      var maxIdx = indices(0)
-      var maxValue = values(0)
+
+      var maxIdx = 0
+      var maxValue = if(indices(0) != 0) 0 else values(0)
 
       foreachActive { (i, v) =>
-        if(v != 0.0 && v > maxValue){
+        if(v > maxValue){
           maxIdx = i
           maxValue = v
         }

mllib/src/test/scala/org/apache/spark/mllib/linalg/VectorsSuite.scala

@@ -91,10 +91,10 @@ class VectorsSuite extends FunSuite {
     val max = vec2.argmax
     assert(max === 3)
 
-    // check for case that sparse vector is created with a zero value in it by mistake
-    val vec3 = Vectors.sparse(5,Array(0, 2, 4),Array(-1.0, 0.0, -.7))
+    // check for case that sparse vector is created with only negative vaues {0.0,0.0,-1.0,0.0,-0.7}
+    val vec3 = Vectors.sparse(5,Array(2, 4),Array(-1.0,-.7))
     val max2 = vec3.argmax
-    assert(max2 === 4)
+    assert(max2 === 0)
   }
 
   test("vector equals") {