title: How to control transparency (alpha) in ggplot violin plot's (dots)
body: <p>The following image</p>
  
  <p><a href="https://i.stack.imgur.com/IzLYw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IzLYw.jpg" alt="enter image description here"></a></p>
  
  <p>Is created with the following code:</p>
  
  <pre><code>library(ggplot2)
  library(plyr)
  library(reshape)
  
  df&lt;- structure(list(variable = structure(c(1L, 1L, 1L, 1L, 1L, 1L,
  1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "bCD.ID.LN", class = "factor"),
      value = c(1.133, 1.068, 1.01, 0.943, 1.048, 1.053, 0.999,
      1.014, 1.149, 1.068, 0.898, 1.008, 0.976, 1.029, 0.95, 0.986,
      1.102, 1.007, 1.08, 1.219), fc_log = c(0.180147861158429,
      0.094911647025467, 0.0143552929770701, -0.0846703239869906,
      0.0676387168753633, 0.0745054363636298, -0.00144341686966872,
      0.0200576523412535, 0.200378797984026, 0.094911647025467,
      -0.15521264992094, 0.0114956388378294, -0.0350469470992008,
      0.0412429822318813, -0.0740005814437769, -0.0203404482841755,
      0.140124223909071, 0.0100636833446975, 0.111031312388744,
      0.285698125958125), len = c(26654L, 26654L, 26654L, 26654L,
      26654L, 26654L, 26654L, 26654L, 26654L, 26654L, 26654L, 26654L,
      26654L, 26654L, 26654L, 26654L, 26654L, 26654L, 26654L, 26654L
      ), ecd = c(0.77027838223156, 0.633263300067532, 0.462219554288287,
      0.290425452089743, 0.577361746829744, 0.592744053425377,
      0.431417423276056, 0.473737525324529, 0.791888647107376,
      0.633263300067532, 0.203909356944549, 0.456929541532228,
      0.367524574172732, 0.519246642155024, 0.3059953477902, 0.395137690402941,
      0.713251294364823, 0.453365348540557, 0.663840324153973,
      0.865123433630975)), .Names = c("variable", "value", "fc_log",
  "len", "ecd"), row.names = c(NA, 20L), class = "data.frame")
  
  
     ggplot(df, aes(x = factor(variable), y=fc_log)) +
      geom_violin(adjust=.5, trim=FALSE, fill='#A4A4A4', color="darkred" ) +
      geom_boxplot(width=0.1) + theme_minimal() +
      ylab("log2(fold change)") +
      xlab("")
  </code></pre>
  
  <p>As stated in the image, how can I make the dots transparent?</p>