Add flow to Series. Add cummul, cummax, cummin for Series with tests

src/es6/__tests__/core/series.js

@@ -589,12 +589,38 @@ describe('series', () => {
       });
     });
 
-    describe('cumsum', () => {
-      const ds = new Series([1, 2, 3, 4, 5], {index: [2, 3, 4, 5, 6]});
-      const ds2 = ds.cumsum();
-      expect(ds2).toBeInstanceOf(Series);
-      expect(ds2.values.toArray()).toEqual([1, 3, 6, 10, 15]);
-      expect(ds2.index.toArray()).toEqual([2, 3, 4, 5, 6]);
+    describe('cumulative functions', () => {
+      it('cumsum', () => {
+        const ds = new Series([1, 2, 3, 4, 5], {index: [2, 3, 4, 5, 6]});
+        const ds2 = ds.cumsum();
+        expect(ds2).toBeInstanceOf(Series);
+        expect(ds2.values.toArray()).toEqual([1, 3, 6, 10, 15]);
+        expect(ds2.index.toArray()).toEqual([2, 3, 4, 5, 6]);
+      });
+
+      it('cummul', () => {
+        const ds = new Series([1, 2, 3, 4, 5], {index: [2, 3, 4, 5, 6]});
+        const ds2 = ds.cummul();
+        expect(ds2).toBeInstanceOf(Series);
+        expect(ds2.values.toArray()).toEqual([1, 2, 6, 24, 120]);
+        expect(ds2.index.toArray()).toEqual([2, 3, 4, 5, 6]);
+      });
+
+      it('cummax', () => {
+        const ds = new Series([1, 2, 6, 4, 5], {index: [2, 3, 4, 5, 6]});
+        const ds2 = ds.cummax();
+        expect(ds2).toBeInstanceOf(Series);
+        expect(ds2.values.toArray()).toEqual([1, 2, 6, 6, 6]);
+        expect(ds2.index.toArray()).toEqual([2, 3, 4, 5, 6]);
+      });
+
+      it('cummin', () => {
+        const ds = new Series([3, 2, 6, 1, 5], {index: [2, 3, 4, 5, 6]});
+        const ds2 = ds.cummin();
+        expect(ds2).toBeInstanceOf(Series);
+        expect(ds2.values.toArray()).toEqual([3, 2, 2, 1, 1]);
+        expect(ds2.index.toArray()).toEqual([2, 3, 4, 5, 6]);
+      });
     });
   });
 });

src/es6/core/frame.js

@@ -348,7 +348,7 @@ export default class DataFrame extends NDFrame {
       return new DataFrame(this._data.set(column, series), this.kwargs);
     else if (series instanceof Immutable.List || Array.isArray(series))
       return new DataFrame(this._data.set(
-        column,
+        column, // $FlowIssue TODO
         new Series(series, {index: this.index, name: column})), this.kwargs);
     throw new TypeError('series must be a Series!');
   }
@@ -804,7 +804,7 @@ export default class DataFrame extends NDFrame {
     csvString += '\r\n';
 
     const updateString = (idx) => {
-      let s = '';
+      let s = ''; // $FlowIssue TODO
       this.columns.forEach((k) => { s += `${this.get(k).iloc(idx)},`; });
       return s;
     };
@@ -1165,7 +1165,7 @@ export default class DataFrame extends NDFrame {
    * // Returns DataFrame([{x: 1, y: -1, z: 2}, {x: -1, y: 1, z: -2}, {x: 2, y: -2, z: 4}])
    * df.cov();
    */
-  cov(): DataFrame {
+  cov(): DataFrame { // $FlowIssue TODO
     return this._pairwiseDataFrame((ds1, ds2) => ds1.cov(ds2));
   }
 
@@ -1184,7 +1184,7 @@ export default class DataFrame extends NDFrame {
    */
   corr(): DataFrame {
     // noinspection Eslint
-    const corrFunc = (ds1, ds2) => {
+    const corrFunc = (ds1, ds2) => { // $FlowIssue TODO
       return ds1.values === ds2.values ? 1 : ds1.corr(ds2);
     };
     return this._pairwiseDataFrame(corrFunc);
@@ -1228,7 +1228,7 @@ export default class DataFrame extends NDFrame {
           if (idx < periods)
             return [k, new Series(Immutable.Repeat(null, this.length).toList(),
               {name: k, index: this.index})];
-          const compareCol = this.get(this.columns.get(idx - periods));
+          const compareCol = this.get(this.columns.get(idx - periods)); // $FlowIssue TODO
           return [k, this.get(k).map((v, vIdx) => v - compareCol.iloc(vIdx))];
         })), {index: this.index});
     }
@@ -1275,6 +1275,7 @@ export default class DataFrame extends NDFrame {
             return [k, new Series(Immutable.Repeat(null, this.length).toList(),
               {name: k, index: this.index})];
           const compareCol = this.get(this.columns.get(idx - periods));
+          // $FlowIssue TODO
           return [k, this.get(k).map((v, vIdx) => (v / compareCol.iloc(vIdx)) - 1)];
         })), {index: this.index});
     }