#* topic_coherence_histogram:
#*   attr:
#*     fillcolor: '3'
#*   desc: Plot a histogram of coherence scores across topics.
#*   ext: R
#*   inputs:
#*   - coherence_by_topic
#* 

topic_coherence_histogram <- function(coherence_by_topic) {
    library(ggplot2)
    library(stringr)

    p <- ggplot(coherence_by_topic) +
         geom_histogram(aes(x = sum_coherence)) +
         scale_x_continuous(name = "Topic Coherence") +
         scale_y_continuous(name = "Number of Topics") +
         theme_bw(16) +
         theme(aspect.ratio = 0.5)

    plot(p)

    coherence_by_topic <- coherence_by_topic[str_order(coherence_by_topic$topic_name, numeric = TRUE), ]
    coherence_by_topic$coherence_z_score <- (coherence_by_topic$sum_coherence - mean(coherence_by_topic$sum_coherence)) / sd(coherence_by_topic$sum_coherence)
    return(coherence_by_topic)

}