Hi,
you can use the Calculator to generate vectors (in my case I have xyz-file input which has the automatic column names coordsX, coordsY, coordsZ, var0, var1, var2) with (var0-coordsX)*iHat+(var1-coordsY)*jHat+(var2-coordsZ)*kHat. If you throw a Glyph filter on the calculator, you can use its Result (Result Array Name) to generate Arrows. If you set the tip length to zero, you have your line segments. Use Result for Orientation and Scale of the Arrow Glyphs.
Hope this helps. Cheers, Venke