Quick Tip: Adding Vertical (or Horizontal) lines to an Excel chart

When using CUSUM's or other charts it may be useful to highlight a period or point through the use of vertical lines. You could draw it on manually, but what if you need to change the graph or the value? With an XY chart it is fairly simple to add a vertical line. Lets say you need to add a vertical dotted line at x=7 and your y-axis scale extends from 0 to 10. Here's how you do it:

1. Add a news series to your graph (right click, "source data", series tab, add)
2. For the x-values enter this: ={7,7}
3. For the y-values enter this: ={0,10}
4. Right click one of the new points eg. x=7, y=10 and format data series
5. Click "auto" for Pattern > line and "none" for Pattern > Marker
6. Change line style to dotted (if you prefer, or keep for solid).
7. Voila!

If you need to make the values variable then just enter the cell reference to pick up:
eg. instead of ={7,7} you would like to use the value in cell B2
You guessed it, just enter ={B2,B2} for the x-values.