update types for NaN columns

Author: risenW

danfojs/src/core/utils.js

@@ -306,11 +306,13 @@ export class Utils {
                 let string_tracker = []
                 let bool_tracker = []
 
-                //remove NaNs from array
+                //remove NaNs from array before checking dtype
                 let arr = []
                 ele.map(val => {
                     if (!(isNaN(val) && typeof val != "string")) {
                         arr.push(val)
+                    }else{
+                        arr.push("NaN") //set NaN to string and return dtype ""string". The caller should explicitly convert the dtype
                     }
                 })
 
@@ -321,6 +323,7 @@ export class Utils {
                         int_tracker.push(false)
                         string_tracker.push(false)
                         bool_tracker.push(true)
+
                     } else if (!isNaN(Number(ele))) {
 
                         if (ele.toString().includes(".")) {

danfojs/tests/core/utils.js

@@ -91,6 +91,11 @@ describe("Utils Functions", function () {
             let result = ['boolean', 'string', 'int32']
             assert.deepEqual(utils.__get_t(data), result)
         })
+        it("Returns string type if values are NaN", function () {
+            let data = [[true, false, true], ["boy", "girl", "boy"], [NaN, undefined, NaN]]
+            let result = ['boolean', 'string', 'string']
+            assert.deepEqual(utils.__get_t(data), result)
+        })
     })
 
     describe("__map_int_to_bool", function () {

package.json

@@ -23,7 +23,7 @@
     "table": "^5.4.6"
   },
   "scripts": {
-    "test": "nyc mocha --require @babel/register danfojs/tests/core/frame",
+    "test": "nyc mocha --require @babel/register danfojs/tests/core/utils",
     "dev": "npm run lint && babel ./danfojs/src -d dist --no-comments",
     "build": "babel ./danfojs/src -d ./dist --no-comments",
     "lint": "eslint ./danfojs/src",