text: import dash_core_components as dcc
  import dash_html_components as html
  import dash_bootstrap_components as dbc
  
  ##==================================
  ## Welcome message
  ##==================================
  message = dbc.Col(
      html.H3(['No page here! Please return to the ', dcc.Link('homepage.', href = '/')], style = dict(textAlign='center')),
      width = dict(size = 8, offset = 2),
  )
  
  navbar = dbc.NavbarSimple(
      [
          dbc.Nav(
              dbc.Row(
                  [
                      # Navigation
                      dbc.NavItem(dbc.NavLink('Lines', href='/')),
                      dbc.NavItem(dbc.NavLink('PCA/LDA', href='/pca')),
                   ],
                   align="center",
                   no_gutters=True,
              ),
          fill = True
          ),
      ],
      brand='  ',
      brand_href="#",
      color="primary",
      id='navBar',
      light = False,
      dark = True,
  )
  
  ##==================================
  ## Assemble layout
  ##==================================
  out = [
      navbar,
      html.Br(),
      message,
  ]
  
  def layout():
      return out
  