Use an XY (Scatter) plot instead of a Line chart.

To add the constant 30 line, add a new column next to your existing data
with 30 in all cells. Then go to Chart Source Data and add the series.




"JaneinPA" wrote in message
...
My students are plotting the temperature of a liquid over time. We can
make
a beautiful line graph, but the scale of the X axis is wrong. It should
show
tick marks at 30 second intervals, but instead it just shows 1, 2, 3, etc.
I
have tried checking off "time scale" when I create the chart, but it uses
the
interval of days, months or years. We want intervals of seconds. Can
this
be done?


Also, is it possible to add straight lines (i.e., y=30) to the line graph?