R package of geographically weighted non-negative principal component analysis

## Reference
- Tsutsumida N., Murakami D.,Yoshida T., Nakaya T. Exploring geographically weighted non negative principal component analysis for producing index. The 27th meeting of GIS association of Japan, Tokyo, 20-21 October, 2018 (Japanese),　http://www.gisa-japan.org/conferences/proceedings/2018/papers/C52.pdf
- Tsutsumida N., Murakami D., Yoshida T., Nakaya T., Lu B., and P. Harris. Geographically Weighted Non-negative Principal Component Analysis for Exploring Spatial Variation in Multidimensional Composite Index, Geocomputation 2019. doi: 10.17608/k6.auckland.9850826.v1

