title: How to scale time on x-axis if the time data is in a character form (R)
body: <p>Here's some of the data:</p>
  
  <pre><code>dput(head(R3L12, 20))
  
  structure(list(Date = c("2015-05-23", "2015-05-23", "2015-05-23", 
  "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", 
  "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", 
  "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", "2015-05-23", 
  "2015-05-23", "2015-05-23"), Time = c("07:25:00", "07:40:00", 
  "07:45:00", "09:10:00", "11:45:00", "11:55:00", "12:05:00", "12:35:00", 
  "12:45:00", "13:30:00", "13:40:00", "13:45:00", "13:55:00", "14:00:00", 
  "14:05:00", "14:10:00", "14:20:00", "14:25:00", "14:30:00", "14:35:00"
  ), Turtle = structure(c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
  3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("R3L1", "R3L11", 
  "R3L12", "R3L2", "R3L4", "R3L8", "R3L9", "R4L8", "R8L1", "R8L4", 
  "R8NAT123"), class = "factor"), HeartRate = c(7.56457, 6.66759, 
  17.51107, 9.72277, 19.44553, 13.07674, 28.115, 14.99467, 17.16947, 
  40.40479, 37.76642, 29.98933, 43.5329, 49.61471, 47.74245, 44.10196, 
  21.35316, 44.68609, 49.25255, 29.98933)), row.names = c(NA, 20L
  ), class = "data.frame")
  </code></pre>
  
  <pre><code>ggplot(R3L12, aes(x=Time, y=HeartRate)) +
    stat_summary(fun.y=mean, geom="point") +
    geom_smooth(aes(x=as.numeric(factor(Time)), y=HeartRate)) +
    labs(title = "Turtle R3L12 Average Heart Rate", ylab = "Heart Rate") +
     theme(axis.text.x = element_text(angle = 90, hjust=1, size = 3, color = "black"), plot.title = element_text(face = "bold", hjust = 0.5, size = 15)) 
  </code></pre>
  
  <p>This is the code I have to graph a scatter plot with a smooth line. I have time intervals from 00:00 to 23:55:00. I only want the times to show up every 30 minutes so the x-axis isn't crowded but I haven't figured out how to do that. I'm very new to R so please keep the explanation simple. </p>
  
  <p>The time variable is currently a character object like this <code>HH:MM:SS</code>. </p>