使用gganimate与geom_sf时的颜色填充异常问题

Let's break down why your animation only shows correct colors at the end, and fix it step by step:

Problem Root Cause #

Your static plot works because you're directly referencing precincts$margin for fill, but when you add transition_states(precincts$margingroup), gganimate splits your data by margingroup for each animation frame. Cross-referencing an external data frame (precincts) inside aes() breaks the per-frame data mapping—only when all frames are rendered (at the end of the animation) do all color values load correctly. Additionally, using precincts$margingroup for the group aesthetic in geom_sf (which uses centroids as its data source) creates a mismatch between the data being plotted and the grouping variable.

Step-by-Step Solution #

1. Align Your Data Frames #

First, merge the margin, margingroup, and dotsize columns from precincts into your centroids data frame. This ensures all variables used in geom_sf's aesthetics are from the same data source:

# Replace "common_id_column" with the shared identifier between centroids and precincts (e.g., precinct ID)
centroids <- centroids %>%
  left_join(precincts %>% select(common_id_column, margin, margingroup, dotsize), 
            by = "common_id_column")

2. Update Static Plot Aesthetics #

Modify your geom_sf call to use columns directly from centroids instead of referencing precincts externally. This keeps the data mapping consistent for animation:

precincts$margingroup <- cut(precincts$margin, breaks = breaks, labels = c(1:37))

# Merge data first (as step 1)
# ...

pointfig <- ggmap(myMap) + 
  geom_sf(data=centroids, aes(fill=margin, group=margingroup), 
          size=dotsize, pch=21, alpha=1, inherit.aes = FALSE) + 
  scale_fill_gradient2(midpoint = 0, low='darkmagenta', mid='white', high='orange', 
                       limits = c(-50,50), oob = scales::squish) + 
  geom_shadowtext(mapping = aes(x = longitude, y = latitude, label = name, vjust=vjust), 
                  data = places, size = 5, fontface = "bold") + 
  labs(fill='Fidesz Margin, %',caption = "Data from valasztas.hu") + 
  ggtitle("Borsod-Abaúj-Zemplén 6th District By-Election by Precinct") + 
  theme_void() + 
  theme(legend.box.just = "center") + 
  theme(plot.title = element_text(size = 12, face = "bold", vjust=4)) + 
  theme(plot.margin = unit(c(1,1,1,1), "cm")) + 
  coord_sf()

(Note: I fixed a typo in scale_fill_gradient2—you had min='white' which should be mid='white' to match the gradient2 syntax)

3. Adjust Animation Code to Use Centroid Data #

Update transition_states to reference the margingroup column in centroids (now part of the data frame used by geom_sf), and tweak shadow_wake to avoid overriding fill colors:

anim <- pointfig + 
  transition_states(margingroup, transition_length = 1, state_length = 0.45, wrap = FALSE) + 
  shadow_wake(wake_length = 0.1, alpha = TRUE, fill = FALSE) # Add fill=FALSE to keep shadow from affecting fill color

The fill=FALSE argument ensures the wake effect only applies to the point's border, not its fill, preventing unintended color distortion during transitions.

4. Verify Ordered States (Optional) #

Ensure margingroup is an ordered factor to guarantee the animation plays in the correct margin order:

centroids$margingroup <- factor(centroids$margingroup, levels = c(1:37), ordered = TRUE)

Testing #

Run the updated code—your animation should now display the correct fill color for each group as it transitions, rather than only at the end.

内容的提问来源于stack exchange，提问作者Owen Winter