HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 49

Auto Scale Auto Scale attempts to fit the best possible vertical scale to the horizontal scale you have chosen. It is not always successful but will often give you a good starting point from which to refine the scale. In the example which follows it is assumed that you have plotted the graph as shown on the previous page. In the PLOT view, press the VIEWS key. Use the arrow keys to scroll down to Auto Scale and press ENTER. The calculator will adjust the y axis in an attempt to fit as much of the graph on to the screen as possible. Some points to bear in mind; • the y axis is scaled only on the first function which has a . • the y axis is scaled for the current x axis (domain) you have chosen in PLOT SETUP. If you've not chosen the domain wisely then your result may not be good. • it doesn't choose 'nice' scales for the y axis such as we would choose (going up in 0.2's or 5's or 10's etc.) so you will generally need to tidy up its choice a little. If you look at the y axis of the graph you've just produced, you'll see that the axis tick marks are so close together that it looks like a solid line. To tidy this up you must change to the PLOT SETUP view. If you look above the PLOT, SYMB and NUM keys you will see the word 'SETUP'. The SETUP view for each of these keys is obtained via the SHIFT key. The values produced by the Auto Scale are shown below, along with a better set that produces a clearer PLOT view. Note particularly the YTick setting that removes the 'thick' effect on the y axis. See "The Expert" chapter beginning on page 62 for more information on how to find good choices for axes. The Auto Scale function is also covered on page 89. 49