K‐means clustering: A half‐century synthesis

Steinley, Douglas

doi:10.1348/000711005x48266

Cited by 854 publications

(615 citation statements)

References 183 publications

(267 reference statements)

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“…To deal with 17 missing values (6.2%) of these difference scores, multiple imputation was applied (Basagaña, Barrera-Gómez, Benet, Antó, & Garcia-Aymerich, 2013) using the R software package developed by Buuren and Groothuis-Oudshoorn (MICE; 2011) to obtain 100 imputed data sets. On these datasets, k-Means cluster analysis (Steinley, 2006) was carried out using the R software package developed by Barrera-Gómez and Basagaña (MICLUST; 2013) to identify clusters of similar patterns of PSS-SR scores. In k-Means clustering an iterative process reallocates participants to a certain number of clusters in order to minimize the within-cluster variance.…”

Section: Methodsmentioning

confidence: 99%

Intensive prolonged exposure therapy for chronic PTSD patients following multiple trauma and multiple treatment attempts

Hendriks

Kleine

Broekman³

et al. 2018

European Journal of Psychotraumatology

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Background: Suboptimal response and high dropout rates leave room for improvement of trauma-focused treatment (TFT) effectiveness in ameliorating posttraumatic stress disorder (PTSD) symptoms. Objective: To explore the effectiveness and safety of intensive prolonged exposure (iPE) targeting chronic PTSD patients with a likely diagnosis of ICD-11 Complex PTSD following multiple interpersonal trauma and a history of multiple treatment attempts. Method: Participants (N = 73) received iPE in 12 × 90-minute sessions over four days (intensive phase) followed by four weekly 90-minute booster prolonged exposure (PE) sessions (booster phase). The primary outcomes, clinician-rated severity of PTSD symptoms, and diagnostic status (Clinician-Administered PTSD Scale; CAPS-IV) were assessed at baseline, post-treatment, and at three and six months. Treatment response trajectories were identified and predictors of these trajectories explored. Results: Mixed model repeated measures analysis of CAPS-IV scores showed a baseline-to-posttreatment decrease in PTSD symptom severity (p < .001) that persisted during the three- and six-month follow-ups with large effect sizes (Cohen’s d > 1.2); 71% of the participants responded. None of the participants dropped out during the intensive phase and only 5% during the booster phase. Adverse events were extremely low and only a minority showed symptom exacerbation. Cluster analysis demonstrated four treatment response trajectories: Fast responders (13%), Slow responders (26%), Partial responders (32%), and Non-responders (29%). Living condition and between-session fear habituation were found to predict outcome. Participants living alone were more likely to belong to the Partial responders than to the Non-responders cluster, and participants showing more between-session fear habituation were more likely to belong to the Fast responders than to the Non-responders cluster. Conclusions: The results of this open study suggest that iPE can be effective in PTSD patients with multiple interpersonal trauma and after multiple previous treatment attempts. In addition, in this chronic PTSD population iPE was safe.

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Section: Methodsmentioning

confidence: 99%

Intensive prolonged exposure therapy for chronic PTSD patients following multiple trauma and multiple treatment attempts

Hendriks

Kleine

Broekman³

et al. 2018

European Journal of Psychotraumatology

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“…Hundreds of classification and partition algorithms can be used to stratify heterogeneity (Lu and Carlin, 2004;Jain, 2009;Jiao et al, 2011). Examples include Kmeans grouping (Steinhaus, 1957;MacQueen, 1967;Steinley, 2006) and regression trees (Breiman et al, 1984), which are implemented in extensively used software packages, ARCGIS (©Esri Inc.) and R/SPODT. The effectiveness of these algorithms is measured by the Calinski-Harabasz pseudo F-statistic (Calinski and Harabasz, 1974), which is a ratio reflecting the within-group similarity and betweengroup differences, and the Gini/Information Gain/Chi-square test, respectively.…”

Section: Introductionmentioning

confidence: 99%

A measure of spatial stratified heterogeneity

Wang

Zhang²,

2016

Ecological Indicators

1,345

608

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a b s t r a c tSpatial stratified heterogeneity, referring to the within-strata variance less than the between stratavariance, is ubiquitous in ecological phenomena, such as ecological zones and many ecological variables. Spatial stratified heterogeneity reflects the essence of nature, implies potential distinct mechanisms by strata, suggests possible determinants of the observed process, allows the representativeness of observations of the earth, and enforces the applicability of statistical inferences. In this paper, we propose a q-statistic method to measure the degree of spatial stratified heterogeneity and to test its significance. The q value is within [0,1] (0 if a spatial stratification of heterogeneity is not significant, and 1 if there is a perfect spatial stratification of heterogeneity). The exact probability density function is derived. The q-statistic is illustrated by two examples, wherein we assess the spatial stratified heterogeneities of a hand map and the distribution of the annual NDVI in China.

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“…W literaturze przedmiotu można znaleźć wiele ilościowych wskaźników jakości grupowania, stworzonych po to, aby ułatwić wybór najlepszej liczby grup (np. [Milligan, Cooper 1985;Rousseeuw 1987;Migdał-Najman, Najman 2005;Steinley 2006]). W tej pracy użyto indeksu Bakera i Huberta, indeksu Huberta i Levine'a oraz indeksu Silhouette Rousseeuw.…”

Section: (X Y) -Najdłuższa Wspólna Podsekwencja (Lcs) Najdłuższy Wsunclassified

Segmentacja łańcuchów środków-celów: miary podobieństwa sekwencji i ilościowe wskaźniki jakości grupowania a wyniki grupowania

Myrda¹

2014

Prace Naukowe Uniwersytetu Ekonomicznego we Wrocławiu

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K‐means clustering: A half‐century synthesis

Cited by 854 publications

References 183 publications

Intensive prolonged exposure therapy for chronic PTSD patients following multiple trauma and multiple treatment attempts

Intensive prolonged exposure therapy for chronic PTSD patients following multiple trauma and multiple treatment attempts

A measure of spatial stratified heterogeneity

Segmentacja łańcuchów środków-celów: miary podobieństwa sekwencji i ilościowe wskaźniki jakości grupowania a wyniki grupowania

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