Flexdashboard - themes and css

Question

I am trying to use different themes to change the flexdashboard look. For some unknown reason the option

output:
    flexdashboard::flex_dashboard:
        theme: <<theme name>>

seem to make no change. The output still looks like default. I even tried to copy css file from flexdashboard directory and put the link directly to the file

output:
    flexdashboard::flex_dashboard:
        css: <<css file>>

but again see no changes. There is also no error when executing rmarkdown::render.

Any ideas

Answer 1

Make sure you've got the indentations right:

output: 
  flexdashboard::flex_dashboard:
    theme: united

Answer 2

---

title: "Sample Dashboard"
output: 
  flexdashboard::flex_dashboard:
    theme: spacelab
    vertical_layout: fill
    orientation: columns
runtime: shiny

---

Available themes include: default, cerulean, journal, flatly, darkly, readable, spacelab, united, cosmo, lumen, paper, sandstone, simplex, yeti.