title: Print two or more inequality signs in the title of a plot
body: <p>I wonder if anyone knows how to print two or more inequality signs in the title of a plot. Note that I do know how to print one inequality sign in the title. See the sample code below:</p>
  
  <pre><code>library(ggplot2)
  df &lt;- data.frame(x = rnorm(10), y = rnorm(10))
  basic.plot &lt;- ggplot(data = df, aes(x = x, y = y)) + 
    geom_point()
  main &lt;- substitute(alpha * " " !=  0)
  plot &lt;- basic.plot + ggtitle(bquote(atop(.(main))))
  plot
  </code></pre>
  
  <p>This gives me a title of "alpha not equal to zero". However, I want my title to be "alpha not equal to beta not equal to zero". I tried the following but failed:</p>
  
  <pre><code>library(ggplot2)
  df &lt;- data.frame(x = rnorm(10), y = rnorm(10))
  basic.plot &lt;- ggplot(data = df, aes(x = x, y = y)) + 
    geom_point()
  main &lt;- substitute(alpha * " " != * beta * " " != 0)
  plot &lt;- basic.plot + ggtitle(bquote(atop(.(main))))
  plot
  </code></pre>
  
  <p>Also note that I have experimented with a Unicode approach but failed as well:</p>
  
  <pre><code>library(ggplot2)
  df &lt;- data.frame(x = rnorm(10), y = rnorm(10))
  basic.plot &lt;- ggplot(data = df, aes(x = x, y = y)) + 
    geom_point()
  main &lt;- c("\u03B1 \u2260 \u03B2 \u2260 0")
  plot &lt;- basic.plot + ggtitle(bquote(atop(.(main))))
  plot
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/C0jPB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C0jPB.png" alt="Unicode approach"></a></p>