bar charts

• How to Add a Line to a Bar Chart
  Overlay a line on a bar chart by aligning values to category centers; use a secondary axis only when units differ and label it clearly.
• How to Set a Colormap for Bars in PGFPlots
  A PGFPlots colormap does not automatically recolor every bar in one ybar plot. Split bars into plots for distinct colors, or set one fill explicitly.