Search results for "Missing data"
showing 3 items of 83 documents
CLUSTERING INCOMPLETE SPECTRAL DATA WITH ROBUST METHODS
2018
Abstract. Missing value imputation is a common approach for preprocessing incomplete data sets. In case of data clustering, imputation methods may cause unexpected bias because they may change the underlying structure of the data. In order to avoid prior imputation of missing values the computational operations must be projected on the available data values. In this paper, we apply a robust nan-K-spatmed algorithm to the clustering problem on hyperspectral image data. Robust statistics, such as multivariate medians, are more insensitive to outliers than classical statistics relying on the Gaussian assumptions. They are, however, computationally more intractable due to the lack of closed-for…
Impact of the terrestrial reference frame on the determination of the celestial reference frame.
2022
Currently three up-to-date Terrestrial Reference Frames (TRF) are available, the ITRF2014 from IGN, the DTRF2014 from DGFI-TUM, and JTRF2014 from JPL. All use the identical input data of space-geodetic station positions and Earth orientation parameters, but the concept of combining these data is fundamentally different. The IGN approach is based on the combination of technique solutions, while the DGFI is combining the normal equation systems. Both yield in reference epoch coordinates and velocities for a global set of stations. JPL uses a Kalman filter approach, realizing a TRF through weekly time series of geocentric coordinates. As the determination of the CRF is not independent of the T…
P-1294 - Utility of the world health organization disability assessment schedule II in schizophrenia
2012
Aim The World Health Organization Disability Assessment Schedule II (WHODAS II) was developed for assessing disability. This study provides data on the validity and utility of the Spanish version of the WHODAS II in a large sample of patients with schizophrenia. Methods The sample included 352 patients with a schizophrenia spectrum disorder. They completed a comprehensive assessment battery including measures of psychopathology, functionality and quality-of-life. A sub-sample of 36 patients was retested after six months to assess its temporal stability. Results Participation in society (6.3%) and Life activities (4.0%) were the domains with the highest percentage of missing data. The intern…