latex graphics

• How to Add a Vertical Line to a TikZ Plot
  Add a vertical line to a PGFPlots graph with a two-point coordinate plot, or draw it in axis coordinates for precise placement.
• Why Does a PGFPlots Cycle List Produce No Colors?
  Define each PGFPlots cycle-list entry as a plot style, select the list by name, and use \addplot+ to preserve its colors when adding options.