Modelling Grocery Retail Topic Distributions: Evaluation, Interpretability and Stability

Understanding the shopping motivations behind market baskets has high commercial value in the grocery retail industry. Analyzing shopping transactions demands techniques that can cope with the volume and dimensionality of grocery transactional data while keeping interpretable outcomes. Latent Dirichlet Allocation (LDA) provides a suitable framework to process grocery transactions and to discover a broad representation of customers' shopping motivations. However, summarizing the posterior distribution of an LDA model is challenging, while individual LDA draws may not be coherent and cannot capture topic uncertainty. Moreover, the evaluation of LDA models is dominated by model-fit measures which may not adequately capture the qualitative aspects such as interpretability and stability of topics. In this paper, we introduce clustering methodology that post-processes posterior LDA draws to summarise the entire posterior distribution and identify semantic modes represented as recurrent topics. Our approach is an alternative to standard label-switching techniques and provides a single posterior summary set of topics, as well as associated measures of uncertainty. Furthermore, we establish a more holistic definition for model evaluation, which assesses topic models based not only on their likelihood but also on their coherence, distinctiveness and stability. By means of a survey, we set thresholds for the interpretation of topic coherence and topic similarity in the domain of grocery retail data. We demonstrate that the selection of recurrent topics through our clustering methodology not only improves model likelihood but also outperforms the qualitative aspects of LDA such as interpretability and stability. We illustrate our methods on an example from a large UK supermarket chain.Comment: 20 pages, 9 figure

Regional Topics in British Grocery Retail Transactions

Understanding the customer behaviours behind transactional data has high commercial value in the grocery retail industry. Customers generate millions of transactions every day, choosing and buying products to satisfy specific shopping needs. Product availability may vary geographically due to local demand and local supply, thus driving the importance of analysing transactions within their corresponding store and regional context. Topic models provide a powerful tool in the analysis of transactional data, identifying topics that display frequently-bought-together products and summarising transactions as mixtures of topics. We use the Segmented Topic Model (STM) to capture customer behaviours that are nested within stores. STM not only provides topics and transaction summaries but also topical summaries at the store level that can be used to identify regional topics. We summarised the posterior distribution of STM by post-processing multiple posterior samples and selecting semantic modes represented as recurrent topics. We use linear Gaussian process regression to model topic prevalence across British territory while accounting for spatial autocorrelation. We implement our methods on a dataset of transactional data from a major UK grocery retailer and demonstrate that shopping behaviours may vary regionally and nearby stores tend to exhibit similar regional demand

Posterior summaries of grocery retail topic models: Evaluation, interpretability and credibility

Understanding the shopping motivations behind market baskets has significant commercial value for the grocery retail industry. The analysis of shopping transactions demands techniques that can cope with the volume and dimensionality of grocery transactional data while delivering interpretable outcomes. Latent Dirichlet allocation (LDA) allows processing grocery transactions and the discovering of customer behaviours. Interpretations of topic models typically exploit individual samples overlooking the uncertainty of single topics. Moreover, training LDA multiple times show topics with large uncertainty, that is, topics (dis)appear in some but not all posterior samples, concurring with various authors in the field. In response, we introduce a clustering methodology that post-processes posterior LDA draws to summarise topic distributions represented as recurrent topics. Our approach identifies clusters of topics that belong to different samples and provides associated measures of uncertainty for each group. Our proposed methodology allows the identification of an unconstrained number of customer behaviours presented as recurrent topics. We also establish a more holistic framework for model evaluation, which assesses topic models based not only on their predictive likelihood but also on quality aspects such as coherence and distinctiveness of single topics and credibility of a set of topics. Using the outcomes of a tailored survey, we set thresholds that aid in interpreting quality aspects in grocery retail data. We demonstrate that selecting recurrent topics not only improves predictive likelihood but also outperforms interpretability and credibility. We illustrate our methods with an example from a large British supermarket chain

Investigating recent environmental change through geomorphological mapping of glacial landforms in Ladakh, India: a geomorphological outreach project

A geomorphological research project was undertaken during a youth expedition to the Indian Himalaya in July - August 2016. The expedition visited the Suru Valley, Ladakh, an area of high altitude desert. The area receives low amounts of precipitation which mostly falls as snow in winter. As a result meltwater (from glaciers and snow) makes a substantial contribution to the discharge of rivers, providing an important water resource for many communities. Most glaciers in the Himalayas are thought to be in a state of negative balance; however a recent study reported that many Himalayan glaciers are stable. These findings are controversial and further studies are needed. The overall aim of this project is to investigate recent glacial and environmental change in the Indian Himalaya by combining geomorphological mapping with recent lacustrine palaeoenvironmental data. The work reported here covers two of the project's objectives: • to produce geomorphological maps from remotely sensed data and field mapping • to engage young people with geomorphological research Prior to the expedition a number of participants mapped the geomorphological features of the wider area from Google Earth imagery. This produced a geomorphological base-map which was ground-truthed on the expedition. Future work will integrate fieldwork with remote sensing to reconstruct the former extent of glaciers in the area, contributing to our understanding of environmental change in the Indian Himalaya. Through their participation in geomorphological research in a challenging wilderness environment this group of young people developed new skills and discovered that science does not only occur in laboratories

Rationale, design and methods for a randomised and controlled trial to evaluate "Animal Fun" - a program designed to enhance physical and mental health in young children

Background: Children with poor motor ability have been found to engage less in physical activities than other children, and a lack of physical activity has been linked to problems such as obesity, lowered bone mineral density and cardiovascular risk factors. Furthermore, if children are confident with their fine and gross motor skills, they are more likely to engage in physical activities such as sports, crafts, dancing and other physical activity programs outside of the school curriculum which are important activities for psychosocial development. The primary objective of this project is to comprehensively evaluate a whole of class physical activity program called Animal Fun designed for Pre-Primary children. This program was designed to improve the child's movement skills, both fine and gross, and their perceptions of their movement ability, promote appropriate social skills and improve social-emotional development. Methods: The proposed randomized and controlled trial uses a multivariate nested cohort design to examine the physical (motor coordination) and psychosocial (self perceptions, anxiety, social competence) outcomes of the program. The Animal Fun program is a teacher delivered universal program incorporating animal actions to facilitate motor skill and social skill acquisition and practice. Pre-intervention scores on motor and psychosocial variables for six control schools and six intervention schools will be compared with post-intervention scores (end of Pre-Primary year) and scores taken 12 months later after the children's transition to primary school Year 1. 520 children aged 4.5 to 6 years will be recruited and it is anticipated that 360 children will be retained to the 1 year follow-up. There will be equal numbers of boys and girls.Discussion: If this program is found to improve the child's motor and psychosocial skills, this will assist in the child's transition into the first year of school. As a result of these changes, it is anticipated that children will have greater enjoyment participating in physical activities which will further promote long term physical and mental health

Day hospital versus admission for acute psychiatric disorders

Backgroun

Day hospital versus out-patient care for psychiatric disorders

Obstacle, adventure and endurance competitions in challenging or remote settings are increasing in popularity. A literature search indicates a dearth of evidence-based research on the organisation of medical care for wilderness competitions. The organisation of medical care for each event is best tailored to specific race components, participant characteristics, geography, risk assessments, legal requirements, and the availability of both local and outside resources. Considering the health risks and logistical complexities inherent in these events, there is a compelling need for guiding principles that bridge the fields of wilderness medicine and sports medicine in providing a framework for the organisation of medical care delivery during wilderness and remote obstacle, adventure and endurance competitions. This narrative review, authored by experts in wilderness and operational medicine, provides such a framework. The primary goal is to assist organisers and medical providers in planning for sporting events in which participants are in situations or locations that exceed the capacity of local emergency medical services resources

Day hospital versus admission for acute psychiatric disorders

BACKGROUND: Inpatient treatment is an expensive way of caring for people with acute psychiatric disorders. It has been proposed that many of those currently treated as inpatients could be cared for in acute psychiatric day hospitals. OBJECTIVES: To assess the effects of day hospital versus inpatient care for people with acute psychiatric disorders. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register (Cochrane Library, issue 4, 2000), MEDLINE (January 1966 to December 2000), EMBASE (1980 to December 2000), CINAHL (1982 to December 2000), PsycLIT (1966 to December 2000), and the reference lists of articles. We approached trialists to identify unpublished studies. SELECTION CRITERIA: Randomised controlled trials of day hospital versus inpatient care, for people with acute psychiatric disorders. Studies were ineligible if a majority of participants were under 18 or over 65, or had a primary diagnosis of substance abuse or organic brain disorder. DATA COLLECTION AND ANALYSIS: Data were extracted independently by two reviewers and cross-checked. Relative risks and 95% confidence intervals (CI) were calculated for dichotomous data. Weighted or standardised means were calculated for continuous data. Day hospital trials tend to present similar outcomes in slightly different formats, making it difficult to synthesise data. Individual patient data were therefore sought so that outcomes could be reanalysed in a common format. MAIN RESULTS: Nine trials (involving 1568 people) met the inclusion criteria. Individual patient data were obtained for four trials (involving 594 people). Combined data suggested that, at the most pessimistic estimate, day hospital treatment was feasible for 23% (n=2268, CI 21 to 25) of those currently admitted to inpatient care. Individual patient data from three trials showed no difference in number of days in hospital between day hospital patients and controls (n=465, 3 RCTs, WMD -0.38 days/month CI -1.32 to 0.55). However, compared to controls, people randomised to day hospital care spent significantly more days in day hospital care (n=265, 3 RCTs, WMD 2.34 days/month CI 1.97 to 2.70) and significantly fewer days in inpatient care (n=265, 3 RCTs, WMD -2.75 days/month CI -3.63 to -1.87). There was no significant difference in readmission rates between day hospital patients and controls (n=667, 5 RCTs, RR 0.91 CI 0.72 to 1.15). For patients judged suitable for day hospital care, individual patient data from three trials showed a significant time-treatment interaction, indicating a more rapid improvement in mental state (n=407, Chi-squared 9.66, p=0.002), but not social functioning (n=295, Chi-squared 0.006, p=0.941) amongst patients treated in the day hospital. Four of five trials found that day hospital care was cheaper than inpatient care (with cost reductions ranging from 20.9 to 36.9%). REVIEWER'S CONCLUSIONS: Caring for people in acute day hospitals can achieve substantial reductions in the numbers of people needing inpatient care, whilst improving patient outcome