  We extends pair distribution function (PDF) analysis into the small-angle
scattering (SAS) regime and describe the data collection protocol for optimum
data quality. We also present the PDFgetS3 software package that can be readily
used to extract the PDF from small-angle scattering data. We then apply the
sasPDF method to investigate structures of some representative nanoparticle
assemblies (NPA) samples with different levels of structural order.
