added captions to unreffed figs in clustering

Author: trevorcampbell

clustering.Rmd

@@ -777,7 +777,7 @@ clustered_data
 Now that we have this information in a tidy data frame, we can make a visualization
 of the cluster assignments for each point, as shown in Figure \@ref(fig:10-plot-clusters-2).
 
-```{r 10-plot-clusters-2, fig.height = 4, fig.width = 4.35, fig.align = "center"}
+```{r 10-plot-clusters-2, fig.height = 4, fig.width = 4.35, fig.align = "center", fig.cap = "The data colored by the cluster assignments returned by K-means."}
 cluster_plot <- ggplot(clustered_data,
   aes(x = flipper_length_mm, 
       y = bill_length_mm, 
@@ -885,7 +885,7 @@ clustering_statistics
 Now that we have `tot.withinss` and `k` as columns in a data frame, we can make a line plot 
 (Figure \@ref(fig:10-plot-choose-k)) and search for the "elbow" to find which value of K to use. 
 
-```{r 10-plot-choose-k, fig.height = 4, fig.width = 4.35, fig.align = "center"}
+```{r 10-plot-choose-k, fig.height = 4, fig.width = 4.35, fig.align = "center", fig.cap = "A plot showing the total WSSD versus the number of clusters."}
 elbow_plot <- ggplot(clustering_statistics, aes(x = k, y = tot.withinss)) +
   geom_point() +
   geom_line() +
@@ -919,7 +919,7 @@ but there is a trade-off that doing many clusterings
 could take a long time.
 So this is something that needs to be balanced.
 
-```{r 10-choose-k-nstart, fig.height = 4, fig.width = 4.35, message= F, warning = F}
+```{r 10-choose-k-nstart, fig.height = 4, fig.width = 4.35, message= F, warning = F, fig.cap = "A plot showing the total WSSD versus the number of clusters when K-means is run with 10 restarts."}
 penguin_clust_ks <- tibble(k = 1:9) |>
   rowwise() |>
   mutate(penguin_clusts = list(kmeans(standardized_data, nstart = 10, k)),