Wordfish mit quanteda (offizielles Quanteda-Tutorial in Englisch)

# 1. Einleitung Dieses Tutorial soll euch die Wordfish-Methode näherbringen. Im Unterschied zur Wordscore-Methode basiert **Wordfish** auf einem unsupervised learning Ansatz. Ähnlich wie bei Wordscore hat sich vor allem das `quanteda`-Team darum bemüht, eine sehr gute `R`-Implementierung zu realisieren. Aus diesem Grund werde ich hier das offizielle Tutorial von der `quanteda` bereitstellen. Die Originalquelle findet ihr [hier](https://tutorials.quanteda.io/machine-learning/wordfish/). # 2. Offizielles WORDFISH-Tutorial Wordfish is a Poisson scaling model of one-dimensional document positions (Slapin and Proksch 2008). Wordfish also allows for scaling documents, but compared to Wordscores reference scores/texts are not required. Wordfish is an unsupervised one-dimensional text scaling method, meaning that it estimates the positions of documents solely based on the observed word frequencies. ```{r eval = T} library(quanteda) library(quanteda.textmodels) library(quanteda.textstats) library(quanteda.corpora) # Die Anleitung zur Installierung findet ihr hier: https://github.com/quanteda/quanteda.corpora library(quanteda.textplots) # Für mehr Infos siehe: https://quanteda.io/articles/pkgdown/examples/plotting.html ``` In this example, we show how to apply Wordfish to the Irish budget speeches from 2010. First, we create a document-feature matrix. Afterwards, we run Wordfish. ```{r eval = T} dfmat_irish <- data_corpus_irishbudget2010 %>% tokens(remove_numbers = TRUE, remove_punct = TRUE,remove_symbols = TRUE) %>% tokens_remove(pattern = stopwords("english")) %>% tokens_tolower() %>% dfm() tmod_wf <- textmodel_wordfish(dfmat_irish, dir = c(6, 5)) summary(tmod_wf) ``` We can plot the results of a fitted scaling model using textplot_scale1d(). ```{r eval = T} textplot_scale1d(tmod_wf) ``` The function also allows to plot scores by a grouping variable, in this case the party affiliation of the speakers. ```{r eval = T} textplot_scale1d(tmod_wf, groups = dfmat_irish$party) ``` Finally, we can plot the estimated word positions and highlight certain features. ```{r eval = T} textplot_scale1d(tmod_wf, margin = "features", highlighted = c("government", "global", "children", "bank", "economy", "the", "citizenship", "productivity", "deficit")) ```