title: Angular 6 : Property 'fromEvent' does not exist on type 'typeof Observable'
body: <p>I am creating sticky navbar directive for sticky header in my angular 6 app </p>
  
  <p>Here is what I have so far:</p>
  
  <pre><code>import { Directive, Input, Renderer, ElementRef, OnInit } from '@angular/core';
  import { Observable } from 'rxjs';
  import { fromEvent } from 'rxjs';
  
  @Directive({
      selector: '[ngStickyNav]'
  })
  
  export class StickyNavDirective implements OnInit {
      private offsetTop: number;
      private lastScroll: number = 0;
      private isSticky: boolean = false;
      @Input('stickyClass') stickyClass: string;
  
      constructor(private elementRef: ElementRef, private renderer: Renderer) {
  
      }
  
      ngOnInit(): void {
          this.offsetTop = this.elementRef.nativeElement.offsetTop;
  
          Observable.fromEvent(window, 'scroll').subscribe(() =&gt; this.manageScrollEvent());
      }
  }
  </code></pre>
  
  <p>I am getting the following error :</p>
  
  <blockquote>
    <p>Property 'fromEvent' does not exist on type 'typeof Observable'.</p>
  </blockquote>
  
  <p>what is wrong with my code? newbie though</p>