This
applet has two functions: First, it can be used to plot user supplied
data. It can also be used to test if a user supplied quadratic function
(a function of the form y = a x^2 + b x + c) fits the
given data by plotting the function. Use it as follows:
 The sequence
of operations must be as follows:
 The user
must enter the data to plot in the DATA area. Though the variables
default to x (the independent variable) and y (the dependent
variable), they can be renamed. Renaming them will cause the
graph to be updated. The values are entered one per line. Error
messages will be displayed in the MESSAGES area if the data
does not have the correct format, that is if the data is not
a number.
 The user
can then plot the data by pressing the "PLOT DATA" button.
 The user
supplies the coefficients defining the function to test.
 The user
plots the function by pressing the "TRY" button.
 The buttons
work as follows:
 CLEAR
will clear the DATA area, the PLOT area and the MESSAGES area.
 PLOT
DATA will plot the data as points.
 TRY
will plot the quadratic function corresponding to the coefficients
supplied by the user.
 The PLOT area
(top, right) will show the plot.
 The MESSAGES
area is used to communicate with the user. Errors will be displayed
there, for example if the number of values is not the same for both
variables. Information will also be displayed there.

