نتایج جستجو برای: روش lda
تعداد نتایج: 375270 فیلتر نتایج به سال:
ÐWe derive a class of computationally inexpensive linear dimension reduction criteria by introducing a weighted variant of the well-known K-class Fisher criterion associated with linear discriminant analysis (LDA). It can be seen that LDA weights contributions of individual class pairs according to the Euclidian distance of the respective class means. We generalize upon LDA by introducing a dif...
نظریه تابعی چگالی یکی از روش های بررسی دستگاه های بس ذره ای است. معروف ترین تقریب هایی که برای جمله تبادلی- همبستگی در این نظریه مطرح است، تقریب چگالی موضعی (lda) و تقریب شیب تعمیم یافته (gga) هستند. اما این دو تقریب برای دستگاه های با الکترون جایگزیده f و d جواب های دقیقی بدست نمی دهند. پس باید سراغ تقریب بهتری به نام lda+u رفت که شکل تصحیح شده تقریب lda است. پارامتر هابارد در این تقریب را می ...
مشکلات موجود در طبقه بند جداساز خطی (lda) از قبیل حساسیت به داده های پرت، فرض اولیه تک مدی بودن توزیع کلاس ها و معکوس ناپذیری ماتریس پراکندگی داخل کلاس انگیزه ای برای ارائه طبقه بندی جدید در این طرح شد. البته در تحقیقات گذشته راهکارهایی همچون استفاده از گراف همسایگی، استفاده از نرم یک و وزنی نمودن طبقه بند برای کاهش حساسیت به داده های پرت، روش هایی مانند کاهش ابعاد، بکارگیری پارامتر تنظیم ساز و...
Relevance-based language models operate by estimating the probabilities of observing words in documents relevant (or pseudo relevant) to a topic. However, these models assume that if a document is relevant to a topic, then all tokens in the document are relevant to that topic. This could limit model robustness and effectiveness. In this study, we propose a Latent Dirichlet relevance model, whic...
Fourier-transform-near infrared (FT-NIR) spectroscopy has been used to develop quantitative and classification models for the prediction of deoxynivalenol (DON) levels in durum wheat samples. Partial least-squares (PLS) regression analysis was used to determine DON in wheat samples in the range of <50-16,000 µg/kg DON. The model displayed a large root mean square error of prediction value (1,97...
Context Among women with a single, recent pregnancy loss, daily preconception low-dose aspirin (LDA) increased the live birth rate with no effect on pregnancy loss. Ovulation is a potential mechanism underlying this effect. Objective We estimated the effect of LDA on the per-cycle risk of anovulation among eumenorrheic women. Design Multicenter, randomized, double-blind, placebo-controlled ...
Background. We investigated the prevalence, symptoms, and QOL impact of esophageal (EI), gastric (GI), and duodenal mucosal injury (DI) individually between low-dose aspirin (LDA) users and nonusers to reveal the clinical features of LDA-related mucosal injury. Methods. Data were extracted from the records of subjects who underwent upper gastrointestinal endoscopy at our department between Apri...
For two-class discrimination, Ref. [1] claimed that, when covariance matrices of the two classes were unequal, a (class) unbalanced dataset had a negative effect on the performance of linear discriminant analysis (LDA). Through re-balancing 10 realworld datasets, Ref. [1] provided empirical evidence to support the claim using AUC (Area Under the receiver operating characteristic Curve) as the p...
This paper establishes a connection between two apparently very different kinds of probabilistic models. Latent Dirichlet Allocation (LDA) models are used as “topic models” to produce a lowdimensional representation of documents, while Probabilistic Context-Free Grammars (PCFGs) define distributions over trees. The paper begins by showing that LDA topic models can be viewed as a special kind of...
The hidden topic model of Chinese text, which possesses complicated semantics, is urgently needed, since China has occupied an increasingly significant role during the booming development of globalization over recent years. This paper details and elaborates the basic process of extracting latent Chinese topics by demonstrating a Chinese topic extraction schema based on Latent Dirichlet Allocati...
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