title: Grouped Frequency Bars in R using ggplot
body: <p>I'm trying to produce a bar graph with frequencies of multiple groups. I tried using geom_bar() but I keep running into "Error: stat_count() must not be used with a y aesthetic." I have one line for each participant, with age (2 categories), condition (2 categories), and their performance (0 or 1). From what I read on the manual and in pretty much everywhere online, if I use</p>
  
  <pre><code>bar&lt;-ggplot(data, aes(age, performance, fill = condition)) + geom_bar(position = "dodge")
  </code></pre>
  
  <p>I should get what I want (<a href="https://i.stack.imgur.com/D20Qz.png" rel="nofollow noreferrer">which is this</a>), but instead I get the error and I can't figure out what I'm missing. Isn't the geom_bar() supposed to give count by default? When I use stat="identity" I get full bars like so: <a href="https://i.stack.imgur.com/EIsYU.png" rel="nofollow noreferrer">how it actually looks</a>.
  Please help! Any advice will be greatly appreciated.</p>
  
  <p>EDITED:
  Here's my actual data:</p>
  
  <pre><code>structure(list(ageyears = c(4L, 4L, 5L, 5L, 5L, 4L, 5L, 4L, 4L, 
  4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 
  4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 4L, 4L, 4L, 4L, 5L, 4L, 
  5L, 5L, 4L, 4L, 4L, 5L, 4L, 4L, 5L, 4L, 5L, 4L, 4L, 5L, 5L, 4L, 
  4L, 5L, 4L, 5L, 4L, 5L, 4L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 
  4L, 4L, 4L, 4L, 4L, 4L, 5L, 4L, 4L, 5L, 5L, 4L, 5L, 5L, 4L, 4L, 
  5L, 5L, 5L, 4L, 5L, 5L, 4L, 5L, 5L, 4L, 4L, 5L, 4L, 5L, 5L, 4L, 
  5L, 4L, 4L, 5L, 5L, 4L, 5L, 5L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 
  5L, 5L, 5L, 4L, 5L, 5L, 4L, 5L, 5L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 
  4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 4L, 5L, 5L, 5L, 
  5L, 5L, 4L, 4L, 4L, 5L, 4L), MatrixLabels = structure(c(2L, 2L, 
  1L, 1L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 
  1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 
  1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 
  1L, 1L, 2L, 2L, 1L, 1L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 
  2L, 2L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("0", 
  "1"), class = "factor"), Mat_sort_pass_fail = c(0L, 0L, 1L, 1L, 
  0L, 0L, 1L, 0L, 1L, 1L, 1L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 
  1L, 1L, 1L, 0L, 0L, 0L, 1L, 0L, 0L, 1L, 1L, 0L, 1L, 1L, 1L, 1L, 
  0L, 0L, 0L, 1L, 0L, 1L, 1L, 0L, 1L, 1L, 0L, 0L, 0L, 0L, 1L, 0L, 
  1L, 0L, 0L, 0L, 0L, 0L, 1L, 1L, 0L, 1L, 1L, 1L, 0L, 1L, 1L, 1L, 
  1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 0L, 1L, 0L, 1L, 0L, 0L, 0L, 0L, 
  1L, 1L, 0L, 0L, 0L, 1L, 1L, 0L, 1L, 1L, 1L, 0L, 0L, 0L, 0L, 0L, 
  0L, 0L, 1L, 0L, 0L, 1L, 1L, 1L, 0L, 0L, 0L, 0L, 1L, 0L, 1L, 1L, 
  0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 0L, 1L, 0L, 1L, 1L, 1L, 1L, 1L, 
  1L, 1L, 1L, 0L, 1L, 1L, 1L, 0L, 1L, 0L, 0L, 0L, 0L, 0L, 1L, 0L, 
  1L, 0L, 0L, 1L, 1L, 1L, 1L, 0L, 1L, 0L, 1L, 0L)), .Names = c("ageyears", 
  "MatrixLabels", "Mat_sort_pass_fail"), row.names = c(1L, 2L, 
  3L, 4L, 5L, 6L, 7L, 8L, 11L, 12L, 13L, 15L, 16L, 17L, 18L, 19L, 
  20L, 21L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 
  34L, 35L, 36L, 37L, 38L, 40L, 41L, 42L, 43L, 44L, 45L, 46L, 48L, 
  49L, 50L, 51L, 52L, 53L, 54L, 55L, 56L, 57L, 58L, 60L, 61L, 62L, 
  63L, 64L, 65L, 66L, 67L, 68L, 69L, 70L, 71L, 72L, 74L, 75L, 76L, 
  77L, 78L, 79L, 80L, 82L, 83L, 85L, 86L, 87L, 88L, 89L, 90L, 91L, 
  92L, 93L, 94L, 95L, 96L, 97L, 98L, 99L, 100L, 101L, 102L, 103L, 
  104L, 105L, 106L, 107L, 108L, 109L, 110L, 111L, 112L, 113L, 114L, 
  115L, 116L, 117L, 118L, 119L, 120L, 121L, 122L, 123L, 124L, 125L, 
  126L, 127L, 128L, 129L, 130L, 131L, 132L, 133L, 134L, 135L, 136L, 
  137L, 138L, 139L, 140L, 141L, 142L, 143L, 144L, 145L, 146L, 147L, 
  148L, 149L, 150L, 151L, 152L, 153L, 154L, 155L, 156L, 157L, 158L, 
  159L, 160L, 197L, 198L, 200L, 201L, 202L, 203L, 204L, 205L, 206L, 
  207L), class = "data.frame")
  </code></pre>