I collect a bunch of data and want to view it as an x-y graph.  So I enter the 
data into a spread sheet, create a chart, and specify "line" as opposed to 
column or pie chart.  The result looks pretty good.

However, after seeing the data, I may want to rescale the X and Y axis and 
adjust the grid lines.  Format >> Axis >> Y-Axis brings up a dialog box with a 
tab for Scale.  This is great, minimum, maximum, grid intervals, and even 
enable or disable tick marks.

Now I want to do the same thing with the X-Axis, but I don't get the tab for 
Scale.  The grid intervals and labels are locked into what I typed on the 
data.  In the sample graph, I have 20 data points, but I would really like to 
have lines for 5, 10, 15, and 20.  Labeling every value makes an unreadible 
clutter.

I tried deleting some entries in the column of X values, but now the graph is 
labeled, "Row 3", "Row 4", etc.  This is even worse.

"Help" tells how to rescale the Y-Axis, exactly as I had been.  It says that 
the X-Axis can be rescaled for X-Y charts.  However XY chart is not one of the 
options under chart type.  Line is the only one that looks reasonable.