Math 174, Spring 2004

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Math 174, Spring 2004

• Graphing Functions

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Plotting Points

• Need to produce graphs that are well-formatted as
  well as informative
• We can have Excel do this for us
• Excel needs many points to graph accurately
• Many is a relative term

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Example 1

• We have a function
• Lets have Excel graph this function over 0,4
• We need values of f(x) to do this how can we
  get them?

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Determining Points for Graph

• Want a large enough number of points arbitrary
  number
• If graph is not pretty, you didnt choose enough
• The text chooses 501 points so it evenly divides
  the interval where x00 and x5004
• Note We have 501 points since we start at x0
• We now have to determine what the distance
  between any 2 adjacent points
• (4-0)/500 0.008
• The distance between any 2 adjacent points is
  0.008

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Graph Examples.xls

• Now that we have the number of points we need
  the distance between any 2 adjacent points, we
  need to have Excel graph the function
• Need to use the IF function to generate y-values
• IF(statement, rule 1, rule 2)
• If the statement is true, IF uses rule 1 else it
  uses rule 2
• We will use rule 1 to be
  and 0 to be rule 2
• Our statement will be
• Lets look at Graph Examples.xls to see how Excel
  graphed the function using our points

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Graphing

• Once we have the values of f(x) that we need, we
  can have Excel generate a graph for us
• Go to Chart Wizard and choose XY Scatter plot,
  with no markers
• We must enter our data range for the y-values and
  then change the series to show the x-values
• Lets try

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Graphing Several Functions

• You can also have Excel graph multiple functions
  on one set of axes
• Doing so helps us understand the connections
  between the quantities that are represented
• Think back to Project 1 Need a Demand curve,
  Revenue curve, Cost curve, and Profit curve
• To do this, you will follow all the previous
  steps that you did to graph one function

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Graphing Several Functions

• You need to determine how many points you need
  for each function you want to graph
• Also, you need to determine the distance between
  any 2 adjacent points
• Have Excel determine the y-values for each
  x-value by using the IF function

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Example 2

• If your functions were
• and you wanted Excel to graph them over 0,2000,
• what would your IF statements be for each?
• Lets see what the graphs look like

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Grahping Utility

• To create your own graphs can be time consuming
  (although very valuable)
• A graphing utility, Graphing.xls, has been
  provided to you in the course files
• Open up the file and follow the directions in the
  blue box
• Note This file contains macros which you need
  to enable if you cannot produce a graph, you
  may not have enabled the macros
• A backup, Graphing BU.xls has also been provided
  (just in case)

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Graphing Macro

• To make sure your macro runs,
• Set your security at medium (prompt) or low
  (automatic) to enable your macro
• Assign your macro
• View Graph toolbar
• Right click on toolbar and left click on
  customize (ignore window that comes up)
• Right click on toolbar again and left click on
  assign macro
• Highlight Graph, hit ok, and close window
• Your macro is now assigned

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Practice

• You should practice working with the graphing
  utility, Graphing.xls
• Use example functions that have been given in the
  text
• You know what these graphs look like
• There are also exercises in the text that you can
  try
• You should know what the graphing utility is
  doing
• Know why you are entering specific items into
  each cell