re-implementing Groupby.js

Author: steveoni

src/danfojs-base/aggregators/groupby.ts

@@ -0,0 +1,78 @@
+import { Console } from "console";
+import DataFrame from "../core/frame"
+import { ArrayType1D, ArrayType2D } from "../shared/types"
+import Utils from "../shared/utils";
+import  concat from "../transformers/concat"
+
+
+/**
+ * The class performs all groupby operation on a dataframe
+ * involving all aggregate funciton
+ * @param {colDict} colDict Object of unique keys in the group by column
+ * @param {keyCol} keyCol Array contains the column names
+ * @param {data} Array the dataframe data
+ * @param {columnName} Array of all column name in the dataframe.
+ * @param {colDtype} Array columns dtype
+ */
+export default class Groupby {
+  colDict?: { [key: string ]: {} }
+  keyCol: ArrayType1D
+  data?: ArrayType2D
+  columnName: ArrayType1D
+  colDtype: ArrayType1D
+  colIndex: ArrayType1D
+  groupDict?: any
+  
+  constructor(keyCol: ArrayType1D, data: ArrayType2D, columnName: ArrayType1D, colDtype:ArrayType1D, colIndex: ArrayType1D) {
+
+    this.keyCol = keyCol;
+    this.data = data;
+    this.columnName = columnName;
+    //this.dataTensors = {}; //store the tensor version of the groupby data
+    this.colDtype = colDtype;
+    this.colIndex = colIndex
+
+  }
+
+  group(): Groupby{
+    this.groupDict = this.data?.reduce((prev, current)=>{
+      function dfs(arr: ArrayType1D, value: ArrayType1D, obj: any) {
+        let firstIndex = arr[0]
+        let remainingndex = arr.slice(1)
+  
+        if(!remainingndex.length) {
+          value.forEach((el, i) => {
+            el = String(el)
+            if (i == firstIndex) {
+              if (el in Object.keys(obj)) {
+                obj[el].push(value)
+              } else {
+                obj[el] = [value]
+              }
+            }
+          });
+        } else {
+          value.forEach((el, i) => {
+            if (i == firstIndex) {
+              el = String(el)
+              if (el as string in obj) {
+                obj[el]  = dfs(remainingndex, value, obj[el])
+              }
+              else {
+                obj[el] = dfs(remainingndex,  value, {})
+              }
+            }
+          })
+        }
+        return obj
+      }
+      
+      prev = dfs(this.colIndex, current, prev)
+      return prev
+
+    }, {})
+
+    delete this.data
+    return this
+  }
+}

src/danfojs-base/core/frame.ts

@@ -24,7 +24,7 @@ import Utils from "../shared/utils"
 import NDframe from "./generic";
 import { table } from "table";
 import Series from './series';
-
+import Groupby from '../aggregators/groupby'
 const utils = new Utils();
 
 /**
@@ -2418,4 +2418,25 @@ export default class DataFrame extends NDframe implements DataFrameInterface {
         }
 
     }
+
+    /**
+     * Groupby
+     * @params col a list of column
+     */
+    groupby(col: Array<string>): Groupby {
+        const columns = this.columns
+        const colIndex = col.map((val) => columns.indexOf(val))
+        const colDtype = this.dtypes.filter((val, index) => {
+            return colIndex.includes(index)
+        })
+
+        return new Groupby(
+            col,
+            this.values as ArrayType2D,
+            columns,
+            colDtype,
+            colIndex    
+        ).group()
+        
+    }
 }