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Custom Plot Functions

The Fixed-Point Conversion tool provides a default time series based plotting function. The conversion process uses this function at the test numerics step to show the floating-point and fixed-point results and the difference between them. However, during fixed-point conversion you might want to visualize the numerical differences in a view that is more suitable for your application domain. For example, plots that show eye diagrams and bit error differences are more suitable in the communications domain and histogram difference plots are more suitable in image processing designs.

You can choose to use a custom plot function at the test numerics step. The Fixed-Point Conversion tool facilitates custom plotting by providing access to the raw logged input and output data before and after fixed-point conversion. You supply a custom plotting function to visualize the differences between the floating-point and fixed-point results. If you specify a custom plot function, the fixed-point conversion process calls the function for each input and output variable, passes in the name of the variable and the function that uses it, and the results of the floating-point and fixed-point simulations.

Your function should accept three inputs:

  • A structure that holds the name of the variable and the function that uses it.

    Use this information to:

    • Customize plot headings and axes.

    • Choose which variables to plot.

    • Generate different error metrics for different output variables.

  • A cell array to hold the logged floating-point values for the variable.

    This cell array contains values observed during floating-point simulation of the algorithm during the test numerics phase. You might need to reformat this raw data.

  • A cell array to hold the logged values for the variable after fixed-point conversion.

    This cell array contains values observed during fixed-point simulation of the converted design.

For example, function customComparisonPlot(varInfo, floatVarVals, fixedPtVarVals).

To use a custom plot function, in the Fixed-Point Conversion tool, select Advanced, and then set Custom plot function to the name of your plot function.

In the programmatic workflow, set the coder.FixptConfig configuration object PlotFunction property to the name of your plot function. See Visualize Differences Between Floating-Point and Fixed-Point Results.