eliminate line in stacked bar ggplot : <p>this graph is made by ggplots but I don't know how to eliminate the lines between the stacked bars (e.g. I want to combine two pink bars into one).   </p>

<p><a href="https://i.stack.imgur.com/YLG7U.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YLG7U.png" alt="enter image description here"></a></p>
