pro Fit - Frequently Asked Questions

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Creating EPS Files (MacOS 9 and earlier)

Q I have problems creating EPS files of a graph. When I create EPS files using pro Fit's "Save" command, the files do not print. When I create the files using the "Print" command and printing into a file, the image does print but is much larger than the graph.

A EPS files are a never ending source of grief. You are facing two separate, distinct problems here.

  1. There are some fonts that do not adhere to the usual standards and they can cause problems when generating EPS files using the "Save" command. Mostly, these are non-standard fonts. If you generate an EPS file through pro Fit and find that it does not print, review the fonts you use and try to substitute them with standard fonts. Alternatively, if you are working on MacOS 9.x, try generating the EPS files using the LaserWriter printer driver (as you did).
  2. Before generating EPS files using the LaserWriter printer driver, choose the command "Preferences ...", select the Printing panel and uncheck the option "Print drawings using PostScript". Then choose "Print" from the File menu, select "File" for destination, go to the "Save as File" panel, and choose the "EPS Mac Standard Preview" format. Now print.

    Disabling the option "Print drawings using PostScript" makes sure that pro Fit uses no Postscript commands while printing. This allows the LaserWriter driver to calculate the rectangle enclosing the printed objects correctly.

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Polar plots

Q How do I create a polar plot with pro Fit?

A The pro Fit package contains a program called "Polar plot", which is located in the folder "Functions & Programs". This program can be used to generate polar plots. To use the program, proceed as follows:

  1. Open the document "Polar plot".
  2. Choose "Compile and Add to Menu" from the Customize menu to add the program to pro Fit's menus.
  3. Open a data window and enter your data points. One column must contain the angles of your data points (in degrees), another column the corresponding radius.
  4. Choose "PolarPlot" from the Prog menu to plot the data points.

For an example of a polar plot, have a look at the file "Polar plot" in the folder "Examples:Plotting - advanced" of your pro Fit package.

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Vector plots

Q I would like to create a vector plot, i.e. a plot that shows a field of vectors (arrows). How can I do this?

A The pro Fit package contains a program called "Plot vector field", which is located in the folder "Functions & Programs". This program can be used for generating vector plots. To use the program, proceed as follows:

  1. Open the document "Plot vector field.
  2. Choose "Compile and Add to Menu" from the Customize menu to add the program to pro Fit's menus.
  3. Open a data window and enter your data points. Prepare the following columns.
    • A column for the x-coordinate of each vector.
    • A column for the y-coordinate of each vector.
    • A column with the length of each vector.
    • A column with the angle (direction) of each vector in radians.
  4. Choose "VectorField" from the Misc menu to plot the data points.

For an example of a vector plot, have a look at the file "Flow plot" in the folder "Examples:Plotting - vector fields" of your pro Fit package. Further comments are provided at the beginning of the file "Plot vector field".

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Batch processing

Q I have a large number of data files, each containing a data set. I want to fit each data set and create a table with all fitted parameters. I can do this by hand, of course, but is there any way to do it automatically?

A Yes, there is. What you want to do is called "batch processing". There are several ways to do this with pro Fit:

For a detailed discussion of this problem, look at the TechNote "Batch processing".

The pro Fit package contains an example for batch processing using an Apple Script. Look at the script file "Batch processing" in the folder "Examples:AppleScript".

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Calculating residuals

Q How do I calculate and plot residuals (i.e. the differences between the fitted function and the data points) after having run a fit?

A To calculate the residuals of a fit, proceed as follows:

  1. Run the fit as usual: Choose Nonlinear Fit from the Calc menu, choose the fit options, and click OK.
  2. When the fit is complete, choose the command Table from the Calc menu. In the dialog box that comes up, set the field "Step" to "points". Then click OK. pro Fit calculates a table that contains the x-values of the fitted data set in the first column, the y-values of the fitted function in the second column, the y-values of the data points in the third column, and the residuals (the differences between the second and third columns) in the fourth column.
  3. Use the residuals in whatever way you want. If you want to view them in the preview window, click into the column number (4) of the residual column while holding down the command key and choose "Y" in the pop-up menu that comes up.
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Fitting differential equations

Q I have a differential equation that describes the behaviour of my experiment. The equation contains several parameters, the values of which I want to calculate by fitting the equation to my experimental data. How can I do this in pro Fit?

A To fit a differential equation (or a set of coupled differential equations), you have to write a pro Fit function that solves the equation(s) numerically. The TechNote " Fitting differential equations" that comes with the pro Fit package in the folder "Notes" contains a detailed discussion on how to do this.

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