Plotrb grouped bar

grouped_bar.rb

require 'plotrb'

data = pdata.name('table').values(
    [
      {category: :A, position: 0, value: 0.1},
      {category: :A, position: 1, value: 0.6},
      {category: :A, position: 2, value: 0.9},
      {category: :A, position: 3, value: 0.4},
      {category: :B, position: 0, value: 0.7},
      {category: :B, position: 1, value: 0.2},
      {category: :B, position: 2, value: 1.1},
      {category: :B, position: 3, value: 0.8},
      {category: :C, position: 0, value: 0.6},
      {category: :C, position: 1, value: 0.1},
      {category: :C, position: 2, value: 0.2},
      {category: :C, position: 3, value: 0.7}
    ]
)

category = pdata.name('category').source('table').transform [facet_transform.keys(:category)]

xs = linear_scale.name('val').from('table.value').nicely.to_width
gs = ordinal_scale.name('cat').from('category.key').padding(0.2).to_height
cs = ordinal_scale.name('color').to_colors
ys = ordinal_scale.name('pos').from('table.position').to_height

rm = rect_mark.from(data) do
  enter do
    y_start { scale(ys).field(:position) }
    height  { scale(ys).use_band }
    x_start { scale(xs).field(:value) }
    x_end   { scale(xs).value(0) }
    fill    { scale(cs).field(:position) }
  end
end

tm = text_mark.from(data) do
  enter do
    y       { scale(ys).field(:position) }
    dy      { scale(ys).mult(0.5).use_band }
    x       { scale(xs).field(:value).offset(-4) }
    text    { scale(xs).field(:value) }
    fill :white
    align :right
    baseline :middle
  end
end

mark = group_mark.from(category) do
  scales gs
  axes y_axis.scale(gs).tick_size(0).tick_padding(8)
  marks rm, tm
  enter do
    y      { scale(gs).field(:key) }
    height { scale(gs).use_band }
  end
end

vis = visualization.width(300).height(240) do
  data data, category
  scales gs, cs, xs, ys
  marks mark
  axes x_axis.scale(xs), y_axis.scale(ys)
end

puts vis.generate_spec(:pretty)

output.txt

$ ruby grouped_bar.rb
/usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/kernel.rb:117:in `method_missing': undefined method `to' for #<Plotrb::Mark:0x007ffb249d2958> (NoMethodError)
	from grouped_bar.rb:37:in `<main>'
Johns-MacBook-Air-2:examples jwoods$ ruby grouped_bar.rb
/usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:586:in `get_full_field_ref': Invalid data field (ArgumentError)
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `block in process_facet_keys'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `collect!'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `process_facet_keys'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:409:in `attribute_post_processing'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:65:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:75:in `block (2 levels) in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `collect'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `block in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `each'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:75:in `block (2 levels) in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `collect'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `block in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `each'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/visualization.rb:41:in `generate_spec'
	from grouped_bar.rb:66:in `<main>'
Johns-MacBook-Air-2:examples jwoods$ ruby grouped_bar.rb
/usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:586:in `get_full_field_ref': Invalid data field (ArgumentError)
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `block in process_facet_keys'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `collect!'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:460:in `process_facet_keys'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/transforms.rb:409:in `attribute_post_processing'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:65:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:75:in `block (2 levels) in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `collect'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `block in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `each'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:75:in `block (2 levels) in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `collect'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:74:in `block in collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `each'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/base.rb:67:in `collect_attributes'
	from /usr/local/var/rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/plotrb-0.0.1/lib/plotrb/visualization.rb:41:in `generate_spec'
	from grouped_bar.rb:66:in `<main>'

Hi John. I think it might be the problem with the facet keys.

A field reference in Plotrb currently does not support symbols. Try facet_transform.keys('category') instead; or facet_transform.keys('data.category'), they should produce the same output.