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### 15.1 Introduction to Plotting

Earlier versions of Octave provided plotting through the use of gnuplot. This capability is still available. But, a newer plotting capability is provided by access to OpenGL. Which plotting system is used is controlled by the `graphics_toolkit` function. See Graphics Toolkits.

The function call `graphics_toolkit ("qt")` selects the Qt/OpenGL system, `graphics_toolkit ("fltk")` selects the FLTK/OpenGL system, and `graphics_toolkit ("gnuplot")` selects the gnuplot system. The three systems may be used selectively through the use of the `graphics_toolkit` property of the graphics handle for each figure. This is explained in Graphics Data Structures. Caution: The OpenGL-based toolkits use single precision variables internally which limits the maximum value that can be displayed to approximately 10^{38}. If your data contains larger values you must use the gnuplot toolkit which supports values up to 10^{308}.