Important Preliminary Information

Item #1

Now that you have begun doing scatter plots, you may occasionally get an error message when doing a regular graph.  If you try to do a graph and see the message to the right, it probably means that you have a StatPlot turned on that references lists that either no longer exist or do not have the same number of entries.

If you get that message, got to <Y=>.  Notice that "Plot1" is highlighted.  Move the cursor onto "Plot1" and press <ENTER>.

Now you'll see that "Plot1" is no longer highlighted.  It has been turned off.  Then try graphing again.  It should work.

Item #2

The calculator graphs functions the same way that we do.  It plots points and connects the dots.  This is usually fine but occasionally it causes potential problems.  Suppose we graph the function shown, using the ZStandard window.

This is what we get.  There are two smooth curves and a nearly vertical portion. 

If you choose <TRACE> and use the left arrow, you'll see the cursor move along the graph.  You'll also see the coordinates of the points on the graph.  Eventually you'll see an x-value of -.8510638.  The next x-value you'll see is -1.06383. 

If you noticed the y-values, you noticed they want from 25.857143 (well above the window shown) to -63.66667 (well below the window shown).  Looking at the function you'll notice it does not exist when x = -1.  The calculator doesn't know this since it only evaluates it at the x-values where the cursor falls. 

It plots the point at (-1.06383, -63.66667) and the point at (-.8510638, 25.857143) and connects those dots, completely ignoring that the function doesn't exist at x = -1.  So, beware when you see nearly vertical portions on graphs.