Physical Sciences and Mathematics Commons^™

Derivatization Of Small Acids To Enhance Sensitivity In Gas Chromatography Mass Spectrometry And Gas Chromatography Vacuum Ultraviolet Spectroscopy, Chih-Hao Wang

Chemistry & Biochemistry Theses - Archive

Disinfection by-products (DBPs) are a significant concern in drinking water quality. Haloacetic acids, which are generated from disinfection processes, are one of the major groups in disinfection by-products. Because they induce potential harmful effects for human health, the US government has already established regulations to control the levels of haloacetic acids in drinking water. In order to control the presence of haloacetic acids in drinking water and monitor other potential harmful compounds, an appropriate analytical method is needed. In this study, a gas chromatography (GC) method was developed for detecting haloacetic acids in water. Three different derivatization reagents were compared …

Method Development For Qualification And Quantification Of Cannabinoids And Terpenes In Extracts By Gas Chromatography-Mass Spectrometry, Allegra Leghissa

Chemistry & Biochemistry Theses - Archive

Cannabinoids are a class of chemical compounds that act on cannabinoid receptors in cells. These receptors have different kinds of ligands, including endocannabinoids (produced in the body by humans and animals), phytocannabinoids (found mainly in Cannabis sativa), and synthetic cannabinoids. At least 85 different phytocannabinoids have been isolated; different cannabinoids are believed to have different effects and possible benefits in medical treatments, and it is therefore fundamental to classify cultivars prior to their medical use. The other class of compounds that characterize C.sativa are terpenes. They confer flavor and fragrance that are unique to each plant and further confer botanical …

Distributed Data Management In Opportunistic Networks, Chance Ray Eary

Computer Science and Engineering Dissertations - Archive

Opportunistic networks (ONs) allow wireless devices, primarily mobile, to interact with one another through a series of opportunistic contacts. While ONs exploit mobility of devices to route messages and distribute information in the absence of dedicated networking infrastructure, the intermittent connections among devices make many traditional computer collaboration paradigms difficult to realize. Two such paradigms are distributed transactions and distributed shared memory (DSM). Distributed transactions are a sequence of operations, executed across multiple nodes, that must successfully complete as specified by its program, or abort with no changes to memory. DSM allows multiple, independent nodes to collectively operate on a …

Numerical Construction Of Diffeomorphism And The Applications To Grid Generation And Image Registration, Xi Chen

Mathematics Dissertations - Archive

Diffeomorphism is an active research topic in differential geometry. In this area, the existence and construction of diffeomorphism under certain constraints is an interesting and meaningful task. J. Moser first proved the existence of diffeomorphism under a Jacobian determinant constraint. Later, Dr. Liao along with his co-authors, proposed the deformation method to construct diffeomorphisms. A div-curl system is created in the construction of diffeomorphisms. Since the Jacobian determinant has a direct physical meaning in grid generation, i.e. the grid cell size, the deformation method was applied successfully to grid generation and adaptation problems. In this dissertation, we review the deformation …

Changes In R, R Core Team

The R Journal

CHANGES IN R 3.3.1 patched

CHANGES IN R 3.3.1

CHANGES IN R 3.3.0

Changes On Cran, Kurt Hornik, Achim Zeileis

The R Journal

In the past 8 months,1322 new packages were added to the CRAN package repository. 43 packages were unarchived,48 archived,1 package had to be removed.The following shows the growth of the number of active packages in the CRAN package repository:

Nonparametric Tests For The Interaction In Two-Way Factorial Designs Using R, Jos Feys

The R Journal

An increasing number of R packages include nonparametric tests for the interaction in two-way factorial designs. This paper briefly describes the different methods of testing and reports the resulting p-values of such tests on datasets for four types of designs: between, within, mixed, and pretest-posttest designs. Potential users are advised only to apply tests they are quite familiar with and not be guided by p-values for selecting packages and tests.

Spatio-Temporal Interpolation Using Gstat, Benedikt Gräler, Edzer Pebesma, Gerard Heuvelink

The R Journal

We present new spatio-temporal geostatistical modelling and interpolation capabilities of the R package gstat. Various spatio-temporal covariance models have been implemented, such as the separable, product-sum, metric and sum-metric models. Inareal-world application we comparespatio temporal interpolations using these models with a purely spatial kriging approach. The target variable of the application is the daily mean PM10 concentration measured at rural air quality monitoring stations across Germany in 2005. R code for variogram fitting and interpolation is presented in this paper to illustrate the workflow of spatio-temporal interpolation using gstat. We conclude that the system works properly and that the …

Model Builder For Item Factor Analysis With Openmx, Joshua N. Pritikin, Karen M. Schmidt

The R Journal

We introduce a shiny web application to facilitate the construction of Item Factor Analysis (a.k.a. Item Response Theory) models using the OpenMx package. The web application assists with importing data, outcome recoding, and model specification. However, the app does not conduct any analysis but, rather, generates an analysis script. Generated Rmarkdown output serves dual purposes: to analyze a data set and demonstrate good programming practices. The app can be used as a teaching tool or as a starting point for custom analysis scripts.

Maps, Coordinate Reference Systems And Visualising Geographic Data With Mapmisc, Patrick E. Brown

The R Journal

The mapmisc package provides functions for visualising geospatial data, including fetching background map layers, producing colour scales and legends, and adding scale bars and orientation arrows to plots. Background maps are returned in the coordinate reference system of the dataset supplied, and inset maps and direction arrows reflect the map projection being plotted. This is a “light weight” package having an emphasis on simplicity and ease of use

Metaplus: An R Package For The Analysis Of Robust Meta-Analysis And Meta-Regression, Ken J. Beath

The R Journal

The metaplus package is described with examples of its use for fitting meta-analysis and meta-regression. For either meta-analysis or meta-regression it is possible to fit one of three models: standard normal random effect, t-distribution random effect or mixture of normal random effects. The latter two models allow for robustness by allowing for a random effect distribution with heavier tails than the normal distribution, and for both robust models the presence of outliers may be tested using the parametric bootstrap. For the mixture of normal random effects model the outlier studies may be identified through their posterior probability of membership in …

Conditional Fractional Gaussian Fields With The Package Fieldsim, Alexandre Brouste, Jacques Istas, Sophie Lambert-Lacroix

The R Journal

We propose an effective and fast method to simulate multidimensional conditional fractional Gaussian fields with the package FieldSim. Our method is valid not only for conditional simulations associated to fractional Brownian fields, but to any Gaussian field and on any (non regular) grid of points.

Statmod: Probability Calculations For The Inverse Gaussian Distribution, Göknur Giner, Gordon K. Smyth

The R Journal

The inverse Gaussian distribution (IGD) is a well known and often used probability distribution for which fully reliable numerical algorithms have not been available. We develop fast, reliable basic probability functions (dinvgauss, pinvgauss, qinvgauss and rinvgauss) for the IGD that work for all possible parameter values and which achieve close to full machine accuracy. The most challenging task is to compute quantiles for given cumulative probabilities and we develop a simple but elegant mathematical solution to this problem. We show that Newton’s method for finding the quantiles of a IGD always converges monotonically when started from the mode of the …

Heteroscedastic Censored And Truncated Regression With Crch, Jakob W. Messner, Georg J. Mayr, Achim Zeileis

The R Journal

The crch package provides functions for maximum likelihood estimation of censored or truncated regression models with conditional heteroscedasticity along with suitable standard methods to summarize the fitted models and compute predictions, residuals, etc. The supported distributions include left- or right-censored or truncated Gaussian, logistic, or student-t distributions with potentially different sets of regressors for modeling the conditional location and scale. The models and their R implementation are introduced and illustrated by numerical weather prediction tasks using precipitation data for Innsbruck (Austria).

Stylometry With R: A Package For Computational Text Analysis, Maciej Eder, Jan Rybicki, Mike Kestemont

The R Journal

This software paper describes ‘Stylometry with R’ (stylo), a flexible R package for the high level analysis of writing style in stylometry. Stylometry (computational stylistics) is concerned with the quantitative study of writing style, e.g. authorship verification, an application which has considerable potential in forensic contexts, as well as historical research. In this paper we introduce the possibilities of stylo for computational text analysis, via a number of dummy case studies from English and French literature. We demonstrate how the package is particularly useful in the exploratory statistical analysis of texts, e.g. with respect to authorial writing style. …

Sbtools: A Package Connecting R To Cloud-Based Data For Collaborative Online Research, Luke A. Winslow, Scott Chamberlain, Alison P. Appling, Jordan S. Read

The R Journal

The adoption of high-quality tools for collaboration and reproducibile research such as R and Github is becoming more common in many research fields. While Github and other version management systems are excellent resources, they were originally designed to handle code and scale poorly to large text-based or binary datasets. A number of scientific data repositories are coming online and are often focused on dataset archival and publication. To handle collaborative workflows using large scientific datasets, there is increasing need to connect cloud-based online data storage to R. In this article, we describe how the new R package sbtools enables direct …

Mclust 5: Clustering, Classification And Density Estimation Using Gaussian Finite Mixture Models, Luca Scrucca, Michael Fop, T Brendan Murphy, Adrian E. Raftery

The R Journal

Finite mixture models are being used increasingly to model a wide variety of random phenomena for clustering, classification and density estimation. mclust is a powerful and popular package which allows modelling of data as a Gaussian finite mixture with different covariance structures and different numbers of mixture components, for a variety of purposes of analysis. Recently, version 5 of the package has been made available on CRAN.This updated version adds new covariance structures, dimension reduction capabilities for visualisation, model selection criteria, initialisation strategies for the EM algorithm, and bootstrap-based inference, making it a full-featured R package for data analysis via …

Gender Prediction Methods Based On First Names With Genderizer, Kamil Wais

The R Journal

In recent years, there has been increased interest in methods for gender prediction based on f irst names that employ various open data sources. These methods have applications from bibliometric studies to customizing commercial offers for web users. Analysis of gender disparities in science based on such methods are published in the most prestigious journals, although they could be improved by choosing the most suited prediction method with optimal parameters and performing validation studies using the best data source for a given purpose. There is also a need to monitor and report how well a given prediction method works in …

Clustering.Sc.Dp: Optimal Clustering With Sequential Constraint By Using Dynamic Programming, Tibor Szkaliczki

The R Journal

The general clustering algorithms do not guarantee optimality because of the hardness of the problem. Polynomial-time methods can find the clustering corresponding to the exact optimum only in special cases. For example, the dynamic programming algorithm can solve the one-dimensional clustering problem, i.e., when the items to be clustered can be characterised by only one scalar number. Optimal one-dimensional clustering is provided by package Ckmeans.1d.dp in R. The paper shows a possible generalisation of the method implemented in this package to multidimensional data: the dynamic programming method can be applied to find the optimum clustering of vectors when only subsequent …

News From The Bioconductor Project, Bioconductor Team

The R Journal

The Bioconductor project provides tools for the analysis and comprehension of high throughput genomic data. The 1211 software packages available in Bioconductor can be viewed at http://bioconductor.org/packages/. Navigate packages using ‘biocViews’ terms and title search. Each package has an html page with a description, links to vignettes, reference manuals, and usage statistics. Start using Bioconductor version 3.3 by installing R 3.3.1 and evaluating the commands

An Interactive Survey Application For Validating Social Network Analysis Techniques, Mitchell Joblin, Wolfgang Mauerer

The R Journal

Social network analysis is extremely well supported by the R community and is routinely used for studying the relationships between people engaged in collaborative activities. While there has been rapid development of new approaches and metrics in this field, the challenging question of validity (how well insights derived from social networks agree with reality) is often difficult to address. We propose the use of several R packages to generate interactive surveys that are specifically well suited for validating social network analyses. Using our web-based survey application, we were able to validate the results of applying community-detection algorithms to infer the …

Conference Report: User! 2016, Joe Rickert

The R Journal

The 12th international R user conference, useR! 2016, took place at Stanford University, Stanford CA fromJune27throughJune30th. Hosted by the Stanford University Department of Statistics and the Stanford Libraries, the conference took place at the Frances Arrillaga Alumni Center, on the surrounding lawns and in several adjacent buildings. The floor to ceiling windows of the larger conference rooms, the garden locations for coffee and meals and the beautiful weather contributed to making the event a classic California experience.

Keyplayer: An R Package For Locating Key Players In Social Networks, Weihua An, Yu-Hsin Liu

The R Journal

Interest in social network analysis has exploded in the past few years, partly thanks to the advancements in statistical methods and computing for network analysis. A wide range of the methods for network analysis is already covered by existent R packages. However, no comprehensive packages are available to calculate group centrality scores and to identify key players (i.e., those players who constitute the most central group) in a network. These functionalities are important because, for example, many social and health interventions rely on key players to facilitate the intervention. Identifying key players is challenging because players who are individually the …

Crowdsourced Data Preprocessing With R And Amazon Mechanical Turk, Thomas J. Leeper

The R Journal

This article introduces the use of the Amazon Mechanical Turk (MTurk) crowdsourcing platform as a resource for R users to leverage crowdsourced human intelligence for preprocessing “messy” data into a form easily analyzed within R. The article first describes MTurk and the MTurkR package, then outlines how to use MTurkR to gather and manage crowdsourced data with MTurk using some of the package’s core functionality. Potential applications of MTurkR include construction of manually coded training sets, human transcription and translation, manual data scraping from scanned documents, content analysis, image classification, and the completion of online survey questionnaires, among others. As …

Exploring Interaction Effects In Two-Factor Studies Using The Hiddenf Package In R., Christopher Franck, Jason A. Osborne

The R Journal

In crossed, two-factor studies with one observation per factor-level combination, interaction effects between factors can be hard to detect and can make the choice of a suitable statistical model difficult. This article describes hiddenf, an R package that enables users to quantify and characterize a certain form of interaction in two-factor layouts. When effects of one factor (a) fall into two groups depending on the level of another factor, and (b) are constant within these groups, the interaction pattern is deemed "hidden additivity" because within groups, the effects of the two factors are additive, while between groups the factors …

Gmdh: An R Package For Short Term Forecasting Via Gmdh-Type Neural Network Algorithms, Osman Dag, Ceylan Yozgatligil

The R Journal

Group Method of Data Handling (GMDH)-type neural network algorithms are the heuristic self organization method for the modelling of complex systems. GMDH algorithms are utilized for a variety of purposes, examples include identification of physical laws, the extrapolation of physical fields, pattern recognition, clustering, the approximation of multidimensional processes, forecasting without models, etc. In this study, the R package GMDH is presented to make short term forecasting through GMDH-type neural network algorithms. The GMDH package has options to use different transfer functions (sigmoid, radial basis, polynomial, and tangent functions) simultaneously or separately. Data on cancer death rate of Pennsylvania from …

The R Journal (August 2016) 8(1): Complete Issue, The R Foundation

The R Journal

Editorial, Michael Lawrence

Contributed Research Articles

metaplus: An R Package for the Analysis of Robust Meta-Analysis and Meta-Regression, Ken J. Beath

Gender Prediction Methods Based on First Names with genderizeR, Kamil Wais

Conditional Fractional Gaussian Fields with the Package FieldSim, Alexandre Brouste, Jacques Istas, and Sophie Lambert-Lacroix

rTableICC: An R Package for Random Generation of 22K and RC Contingency Tables, Haydar Demirhan

Maps, Coordinate Reference Systems and Visualising Geographic Data with mapmisc, Patrick E. Brown

Variable Clustering in High-Dimensional Linear Regression: The R Package clere, Loïc Yengo, Julien Jacques, Christophe Biernacki, and Mickael Canouil

Stylometry with R: A Package for …

Editorial, Bharath Sriraman

The Mathematics Enthusiast

No abstract provided.

Tme Volume 13, Number 3

The Mathematics Enthusiast

No abstract provided.

The Secret Life Of 1/N: A Journey Far Beyond The Decimal Point, Christopher Lyons

The Mathematics Enthusiast

The decimal expansions of the numbers 1/n (such as 1/3 = .03333..., 1/7 = 0.142857...) are most often viewed as tools for approximating quantities to a desired degree of accuracy. The aim of this exposition is to show how these modest expressions in fact have much more to offer, particularly in the case when the expansions are infinitely long. First we discuss how simply asking about the period (that is, the length of the repeating sequence of digits) of the decimal expansion of 1/n naturally leads to more sophisticated ideas from elementary number theory, as well as to …