title: Keep points in gganimate
body: <p>I would like to document the progress in a test situation using gganimate:
  I have come so far:</p>
  
  <pre><code>library(tidyverse)
  library(gganimate)
  
  data &lt;- tribble(~user, ~agree, ~accord, ~messung,
              "1", .8, .9, 1,
              "2",.7, .8, 1,
             "3", .6, .9, 1)
  data2 &lt;- tribble(~user, ~agree2, ~accord2, ~messung2,
             "1",  .4, .7, 2,
              "2", .5, .9, 2,
              "3", .9, .9, 2)
  
  data%&gt;%
  left_join(data2)%&gt;%
   mutate(user = as.numeric(user))%&gt;%
   ggplot(aes(x = accord, y = agree))+
   geom_point(aes(fill = "grey"), color = "grey", size = 2)+
   geom_point(aes(x = accord2, y = agree2), color = "green",
           size = 2)+
   xlim(0,1)+
   ylim(0,1)+
   geom_segment(aes(x = accord,
                 y = agree,
                 xend = accord2,
                 yend = agree2),
             size = 0.5, arrow = arrow(type="closed", length =
                                         unit(.08, "inches"), angle = 30), 
  color = "grey")+
  theme_minimal()+
  guides(fill=FALSE, color=FALSE)+
  transition_manual(user)
  </code></pre>
  
  <p>The colours and representations are of secondary importance at first. It would be important to learn how to animate the points one after the other without the previous points disappearing again? 
  Any help is welcome! Thanks</p>