Comment 1 for bug 492103

1) Any contributions would be very welcome! You don't need to download the source if you want to work on enhancing the function plotter extension: it is a python script that is installed with the default Inkscape 0.47 distribution. Depending on your OS you can find it in these default locations:
 linux: /usr/share/inkscape/extensions/funcplot.py
 osx: /Applications/Inkscape.app/Contents/Resources/extensions/funcplot.py
 win32: [installation directory of inkscape]\share\extensions\funcplot.py

Links to the 0.47 release branch source code repository:
Python script:
<http://bazaar.launchpad.net/%7Einkscape.dev/inkscape/RELEASE_0_47_BRANCH/annotate/head%3A/share/extensions/funcplot.py>
Extension definition file:
<http://bazaar.launchpad.net/%7Einkscape.dev/inkscape/RELEASE_0_47_BRANCH/annotate/head%3A/share/extensions/funcplot.inx>

2) the term 'clipping' is problematic for what you miss in the output of the function plotter: 'clipping' in Inkscape refers to the implementation of the SVG feature described in the SVG spec (http://www.w3.org/TR/SVG11/masking.html#ClippingPaths).

3) I agree that the output of the function plotter seems inconsistent: the x and y axis (if drawn) are limited to the area of the initial rectangle whereas the function curve itself, when rendered for values between the entered 'Start X value' and 'End X value', is not. AFAIU the requested "Y clipping" is implemented by adjusting the Y values of the rectangle's top and bottom so that the output lies within the rectangle.