title: how do I avoid NaN on the axis of a scatter plot ggplot2
body: <p>This is my first post as an R-newbie. Please be patient with me :-)</p>
  
  <p>I am plotting some measurement data (Velo), which I transformed into a dataframe (mdata).
  I cannot change the fact that some values in the data is NaN/NA/empty.</p>
  
  <p>Data (Velo):</p>
  
  <pre><code>   Location Height MeanVelocity
  1    Middle    0.1           NA
  2    Middle    0.1           NA
  3    Middle    0.1           NA
  4    Middle    1.1           NA
  5    Middle    1.1           NA
  6    Middle    1.1         0.00
  7    Middle    0.6           NA
  8    Middle    0.6           NA
  9    Middle    0.6         0.07
  10   Middle    0.1           NA
  11   Middle    0.1           NA
  12   Middle    0.1           NA
  13   Middle    0.1         0.29
  14   Window    0.1           NA
  15   Window    0.1           NA
  16   Window    0.1           NA
  17   Window    1.1           NA
  18   Window    1.1           NA
  19   Window    1.1         0.00
  20   Window    0.6           NA
  21   Window    0.6           NA
  22   Window    0.6           NA
  23   Window    0.6           NA
  24   Window    0.6         0.05
  25   Window    0.1           NA
  26   Window    0.1           NA
  27   Window    0.1         0.11
  </code></pre>
  
  <p>When I make a scatter plot, the "Na" is seen on the y-axis. How do I avoid this?</p>
  
  <p>The code:</p>
  
  <pre><code>Velo
  mdata &lt;- melt(Velo, id=c("Location","Height"))
  mdata
  ggplot(data=mdata, aes(x=value, y=Height, group=1)) + 
    geom_errorbarh(aes(xmin = ifelse(value - 0.05 &lt;0, 0, value - 0.05), xmax = value + 0.05, height=.2)) +
    geom_line(colour="grey", linetype="dotted", size=1.1) +
    geom_point(colour="black", size=4, shape=21, fill="white") +
    xlab("(3 min) Air Velocity [m/s]") + ylab("Height [m]") +
    xlim(-0.1,0.5) +
    facet_grid(.~Location)     
  </code></pre>