title: Changing the scale of x-axis using scale_x_continuous
body: <p>I am creating a scatter plot using ggplot2. The default gives me an x axis that has every value form 0 to 30. I'd prefer to have it go by 5s or something like that. I have been trying to use scale_x_continuous(), but I get this:<br>
  Error: Discrete value supplied to continuous scale</p>
  
  <p>Here is the code that I am trying to work with:</p>
  
  <pre><code>Daily.Average.plot &lt;- ggplot(data = Daily.average, aes(factor(Day), Mass))+
    geom_point(aes(color = factor(Temp))) + 
    scale_x_continuous(breaks = seq(0,30,5))
  
  Daily.Average.plot
  </code></pre>
  
  <p>When I run this without the scale_x_continuous I get a graph that looks fine with no errors, just the incorrect x axis. All of the columns in the data set are numeric when I check str(), if that matters. Do I have an error in my code, or should I be using something different to change the scale?</p>
  
  <p>Here is a sample of my data set:</p>
  
  <pre><code>N   Day       Mass Temp
  1    1 0.00000000    5
  2    2 0.00000000    5
  3    3 0.07692308    5
  4    4 0.07692308    5
  5    5 0.07692308    5
  6    6 0.15384615    5
  7    7 0.15384615    5
  8    8 0.23076923    5
  9    9 0.38461538    5
  10  10 0.46153846    5
  11   1 0.00000000   10
  12   2 0.00000000   10
  13   3 0.00000000   10
  14   4 0.09090909   10
  15   5 0.09090909   10
  16   6 0.54545455   10
  17   7 0.54545455   10
  18   8 0.63636364   10
  19   9 0.90909091   10
  20  10 1.36363636   10
  21   1 0.00000000   15
  22   2 0.07692308   15
  23   3 0.61538462   15
  24   4 0.76923077   15
  25   5 0.76923077   15
  26   6 1.23076923   15
  27   7 1.69230769   15
  28   8 2.07692308   15
  29   9 2.46153846   15
  30  10 3.07692308   15
  </code></pre>