Create a GUI that has A button to bring up a dialog to select a text file and read it in.
Plot the x,y values on the GUI Have text entry values, one for each parameter, in which to enter guesses for the parameters. A button that calls the fminsearch command with appropriate arguments to do a non-linear fit to the data. Display the best fit values of the parameters Draw a calculated y vector on the graph.
Your functions should be well commented, indented (to highlight loops or if statements), and the variables should have consistent and meaningful names.