title: Line plot with gray and black dotted lines
body: <p>With the ggplot2 R package I made a line plot with 6 colored lines (referred to 6 levels of a factor), and I would like to change it in black and white, making 3 BLACK solid, dashed and dotted lines plus 3 GREY solid, dashed and dotted lines.
  I try with scale_linetype_manual() and scale_color_grey() but I'm not able to mix the grey and black dotted lines.</p>
  
  <p>Here the code of the scale grey option:</p>
  
  <pre><code>ggplot() + 
    geom_line(data = f[!is.na(f$fr),], aes(x=date2, y=fr, colour=locality, group=locality), 
              size = 1.0) + 
    scale_color_grey(start = 0, end = 0.9, guide="legend", name="Locality", 
                     labels=c("a","b","c","d","e","f")) + 
    xlab("") + 
    ylab("") + 
    theme_bw() +
    theme(legend.position = "top", panel.background = element_rect(fill = "white"), 
          panel.grid.major = element_line(colour = "white"), 
          axis.text.x=element_text(angle=90,hjust=1,vjust=0.5)) + 
    facet_grid(.~year)    
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/rrKed.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rrKed.jpg" alt="enter image description here"></a></p>
  
  <p>while this is the code with dotted lines:</p>
  
  <pre><code>ggplot() + 
    geom_line(data = f[!is.na(f$fr),], aes(x=date2, y=fr, linetype=locality, group=locality), 
              size = 1.0) + 
    scale_linetype_manual(name="Locality", 
                          values=c("solid", "dashed", "dotted", "dotdash", "longdash", "twodash"), 
                          labels=c("a","b","c","d","e","f")) +
    xlab("") + 
    ylab("") + 
    theme_bw()+ 
    theme(legend.position = "top", panel.background = element_rect(fill = "white"), 
          panel.grid.major = element_line(colour = "white"), 
          axis.text.x=element_text(angle=90,hjust=1,vjust=0.5)) +
    facet_grid(.~year)    
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Pb9a9.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Pb9a9.jpg" alt="enter image description here"></a></p>
  
  <p>so.. Someone can help me to create this same plot with one solid black line, one dashed black line, one dotted black line, one solid grey line etc.?</p>