Comparative study of different B-spline approaches for functional data

The sample observations of a functional variable are functions that come from the observation of a statistical variable in a continuous argument that in most cases is the time. But in practice, the sample functions are observed in a finite set of points. Then, the first step in functional data analysis is to reconstruct the functional form of sample curves from discrete observations. The sample curves are usually represented in terms of basis functions and the basis coefficients are fitted by interpolation, when data are observed without error, or by least squares approximation, in the other case. The main purpose of this paper is to compare three different approaches for estimating smooth sample curves observed with error in terms of B-spline basis: regression splines (non-penalized least squares approximation), smoothing splines (continuous roughness penalty) and P-splines (discrete roughness penalty). The performance of these spline smoothing approaches is studied via a simulation study and several applications with real data. Cross-validation and generalized cross-validation are adapted to select a common smoothing parameter for all sample curves with the roughness penalty approaches. From the results, it is concluded that both penalized approaches drastically reduced the mean squared errors with respect to the original smooth sample curves with P-splines giving the best approximations with less computational cost.Project MTM2010-20502 from Dirección General de Investigación, Ministerio de Educación y Ciencia SpainProject P11-FQM-8068 from Consejería de Innovación, Ciencia y Empresa. Junta de Andalucía, Spai

Prediction of functional data with spatial dependence: a penalized approach

This paper is focus on spatial functional variables whose observations are a set of spatially correlated sample curves obtained as realizations of a spatio-temporal stochastic process. In this context, as alternative to other geostatistical techniques (kriging, kernel smoothing, among others), a new method to predict the curves of temporal evolution of the process at unsampled locations and also the surfaces of geographical evolution of the variable at unobserved time points is proposed. In order to test the good performance of the proposed method, two simulation studies and an application with real climatological data have been carried out. Finally, the results were compared with ordinary functional kriging.Project P11-FQM-8068 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, SpainProjects MTM2013-47929-P, MTM2011-28285-C02-C2 and MTM 2014-52184-P from Secretaría de Estado Investigación, Desarrollo e Innovación, Ministerio de Economía y Competitividad, Spai

Functional PCA and Base-Line Logit Models

In many statistical applications data are curves measured as functions of a continuous parameter as time. Despite of their functional nature and due to discrete time observation, these type of data are usually analyzed with multivariate statistical methods that do not take into account the high correlation between observations of a single curve at nearby time points. Functional data analysis methodologies have been developed to solve these type of problems. In order to predict the class membership (multi-category response variable) associated to an observed curve (functional data), a functional generalized logit model is proposed. Base-line category logit formula- tions will be considered and their estimation based on basis expansions of the sample curves of the functional predictor and parameters. Functional principal component analysis will be used to get an accurate estimation of the functional parameters and to classify sample curves in the categories of the response variable. The good performance of the proposed methodology will be studied by developing an experimental study with simulated and real data.Projects MTM2010-20502 from Dirección General de Investigación del MEC SpainFQM-08068 from Consejería de Innovación, Ciencia y Empresa de la Junta de Andalucía Spai

Schizotypal personality and semantic functioning: Revisiting category fluency effects in a subclinical sample

Semantic disturbances have been proposed as a possible cause of formal thought disorder in schizophrenia. Fluency tasks, in which volunteers are asked to produce as many exemplars as they can for a given category during one minute, are usually applied to the assessment of semantic processing. However, studies associating fluency and proneness to psychosis have provided conflicting results so it is not clear whether these disturbances can be identified at subclinical stages. We conducted two experiments. In the first one, 71 volunteers completed written category fluency tasks with four semantic categories (animals, fruits, clothing and vehicles). In the second experiment, 77 new participants completed oral category and phonological fluency tasks (words starting with f, t, p and c). In both experiments, we assessed schizotypal personality and vocabulary size. Schizotypal traits were not reliably associated with either productivity or originality of the responses in any experiment. In contrast, vocabulary size significantly predicted the participants' scores in all the tasks. Along with results of other recent studies, our data cast doubt on the reliability of previous observations pointing out an association between schizotypy and lexical-semantic disturbances, at least in relation to productivity and originality in fluency tests

On the estimation of functional random effects

Functional regression modelling has become one of the most vibrant areas of research in the last years. This discussion provides some alternative approaches to one of the key issues of functional data analysis: the basis representation of curves, and in particular, of functional random effects. First, we propose the estimation of functional principal components by penalizing the norm, and as an alternative, we provide an efficient and unified approach based on B-spline basis and quadratic penalties

Estudio comparativo de las habilidades sociales de niños con trastorno de Asperger con niños y niñas de desarrollo normotípico en edades de 6 a 8 años integrados en Educación Primaria

En el marco de las competencias sociales, pretendemos analizar y comparar las habilidades sociales que presentan un grupo con Trastorno de asperger y otro normotípico de niñas y niños en edades y nivel de escolaridad equivalente. Los participantes fueron 20, 10 con trastorno Asperger y 10 normotípicos, de edades entre 6 y 8 años, cursando entre el primero a tercero básico (primaria). Ambos grupos fueron equiparados en Edad Cronológica y Cociente Intelectual. Se evaluaron los dos grupos con el CHIS (Monjas, 2009a). Utilizamos un diseño no experimental, ex-post-facto. Para comparar la muestra y comprobar las hipótesis aplicamos la t de student. Concluimos que el grupo con Trastorno de Asperger presenta menores habilidades sociales en las seis subescalas que el grupo normotípico. Palabras claves: Habilidades sociales, Trastorno de Asperger, Trastorno Espectro AutistaMáster en Investigación Aplicada a la Educació

Concordancia entre los códigos CIE9MC y los criterios clínicos en la identificación de pacientes pluripatológicos

La mayor expectativa de vida en la edad adulta es un logro de las sociedades industrializadas que se ha propiciado por distintos mecanismos: mejora del nivel económico de la población, medidas de salud pública, medidas sociales y desarrollo de los recursos sanitarios asistenciales. No obstante, la muerte es inherente a la existencia del hombre la muerte, precedida en un alto porcentaje de casos de enfermedades crónicas y perfil de paciente pluripatológico, que limitan en mayor o menor medida las actividades del paciente, y que suponen un gran reto para los sistemas sanitarios. A lo largo de la segunda mitad del siglo XX, y especialmente a finales de dicho siglo y principios del actual, la proporción de enfermos crónicos que precisan asistencia sanitaria de diversa índole está creciendo de forma preocupante. Es la contrapartida al logro social de la mayor expectativa de vida. Se viven más años sí, pero también hay más cronicidad. El envejecimiento de la población en los países occidentales conlleva un incremento de las enfermedades crónicas, del perfil de paciente pluripatológico o frágil y las agudizaciones que afectan a la supervivencia y provocan ingresos repetidos. Se puede caracterizar nuestra situación en los siguientes rasgos: Transición demográfica: En los países desarrollados la población envejece, en España a un ritmo muy acusado. Transición epidemiológica: que se traduce en un incremento de la prevalencia de condiciones crónicas y de la multimorbilidad. Impacto económico sobre el sistema sanitario: Cronicidad, pluripatología y multimorbilidad tienen una gran repercusión en los costes del sistema sanitario. Por tanto el binomio comorbilidad y edad avanzada se perfila como realidad emergente, compleja, a la que la sociedad en general y sistemas de salud en particular han de dar respuesta. Este grupo de pacientes es especialmente susceptible a sufrir los efectos negativos de una atención superespecializada y fragmentada, donde además de ser ineficaz en la atención a estos enfermos se hace insostenible desde el punto de vista económico y social

Positive schizotypy increases the acceptance of unpresented materials in false memory tasks in non-clinical individuals

Enhanced spreading of semantic activation has been hypothesized to underlie some of the most significant symptoms of schizotypal personality, like thought disorder, odd speech, delusion, or magical thinking. We applied the Deese/Roediger-McDermott false memory task to the study of semantic activation in a group of 123 non-clinical individuals varying in the three dimensions of schizotypal personality: positive, negative and disorganized schizotypy. In the study phase, we presented them with lists composed of words semantically associated to unpresented critical words. Then, they responded to a recognition questionnaire including previously presented words and critical unpresented lures, as well as weakly related and unrelated unpresented lures. Participants rated their confidence in recognizing each word. They also filled in a standardized schizotypal personality questionnaire. Confirming the false memory effect, recognition ratings provided in response to critical words were higher than those produced for both weakly related and unrelated items. Crucially, scores in the positive dimension increased recognition percentages and confidence ratings for weakly related and unrelated lures. This study indicates that high levels of positive schizotypy might influence the tendency to accept false memories of unrelated unpresented material

Semantic priming and schizotypal personality: reassessing the link between thought disorder and enhanced spreading of semantic activation

The term schizotypy refers to a group of stable personality traits with attributes similar to symptoms of schizophrenia, usually classified in terms of positive, negative or cognitive disorganization symptoms. The observation of increased spreading of semantic activation in individuals with schizotypal traits has led to the hypothesis that thought disorder, one of the characteristics of cognitive disorganization, stems from semantic disturbances. Nevertheless, it is still not clear under which specific circumstances (i.e., automatic or controlled processing, direct or indirect semantic relation) schizotypy affects semantic priming or whether it does affect it at all. We conducted two semantic priming studies with volunteers varying in schizotypy, one with directly related prime-target pairs and another with indirectly related pairs. Our participants completed a lexical decision task with related and unrelated pairs presented at short (250 ms) and long (750 ms) stimulus onset asynchronies (SOAs). Then, they responded to the brief versions of the Schizotypal Personality Questionnaire and the Oxford-Liverpool Inventory of Feelings and Experiences, both of which include measures of cognitive disorganization. Bayesian mixed-effects models indicated expected effects of SOA and semantic relatedness, as well as an interaction between relatedness and directness (greater priming effects for directly related pairs). Even though our analyses demonstrated good sensitivity, we observed no influence of cognitive disorganization over semantic priming. Our study provides no compelling evidence that schizotypal symptoms, specifically those associated with the cognitive disorganization dimension, are rooted in an increased spreading of semantic activation in priming tasks