Building a climate risk dashboard - server (output)

Communicating climate risk

FEMA has asked us to build an improved dashboard that visualizes the risk of climate change in the United States.

Based on your submitted designs and our skill level, we will work to implement this Shiny dashboard.

Construct the server (output)

National map

• Create the national map and store it in output$national_map. Use the provided templated code to get started.
• Add a message() to print an informative message in the console whenever output$national_map is rendered. Using message() and warning() functions makes it much easier to troubleshoot the app.
• Render the dashboard and test the national map. Does it work as expected?

Starter code to generate the national map

Fill in the TODOs and correctly integrate into the server code chunk.

# visualize the risks nationally
ggplot(data = climate_sf) +
  # layer for each county's risk
  geom_sf(mapping = aes(fill = TODO)) +
  # layer for state boundaries to better locate regions
  geom_sf(data = state_sf, fill = NA, color = "white") +
  # appropriate color palette
  scale_fill_discrete_diverging(rev = TRUE) +
  # don't label the legend
  labs(
    fill = NULL
  ) +
  # map theme
  theme_map(base_size = 18) +
  # position the legend on the right
  theme(legend.position = "right")

Tip

To access input values which are character strings and treat them as column names, use the bang-bang operator. For example, if input$var_name contained the name of a column and you wanted to use it in a ggplot2 visualization, you could write your code like:

```{r}
#| context: server

output$myplot <- renderPlot({
  ggplot(data = df, mapping = aes(x = !!input$var_name)) +
    geom_histogram()
})
```

County map

• Create the highlighted county map and store it in output$county_map. Use the provided templated code to get started.
• Add a message() to print an informative message in the console whenever output$county_map is rendered. Using message() and warning() functions makes it much easier to troubleshoot the app.

Starter code to generate the national map

Fill in the TODOs and correctly integrate into the server code chunk.

# get selected county's state
county_state <- climate_sf |>
  filter(county == TODO) |>
  pull(STATE_NAME)

climate_sf |>
  # filter for counties in specific state
  filter(STATE_NAME == county_state) |>
  # variable to highlight selected county
  mutate(selected = county == TODO) |>
  # draw the map
  ggplot() +
  geom_sf(mapping = aes(fill = selected, color = selected)) +
  scale_fill_manual(values = c(NA, "orange")) +
  scale_color_manual(values = c("white", "orange")) +
  theme_map() +
  theme(legend.position = "none")

Validating inputs

What happens if there is no county provided in the input? Cryptic red error messages in the UI can be disconcerting to users. Instead, we can use validate() and need() to shunt the error messages to the console and print a human-readable message to the user.

For example, say the output relies on input$num which must not be empty. We can use

need(input$num, "Provide a number")

to check if input$num is provided. If the condition fails (i.e. input$num is blank or missing), then need() returns the specified character string. We can incorporate these requirements into the output using validate().

output$myplot <- renderPlot({
  validate(
    need(input$num, "Provide a number")
  )
  
  # remaining code...
})

validate() takes any number of arguments depending on how many conditions must be checked. If any of them fail, the app triggers an error which is reported in the console and displays the need()-provided message to the user in the UI.

• Add an appropriate validation check to output$county_map that ensures the user has provided a specific county.

County risk scores

selected_county

• We will need to repeatedly query the climate_risk data frame for specific information on selected counties. Rather than repeat this process, instead create selected_county which is a filtered copy of the climate_risk data frame for the specified county.
• Add an appropriate validation check to selected_county that ensures the user has provided a specific county.

County stats for value boxes

Use the filtered data frame to generate the text strings for each of the value boxes.

• Overall risk
• Expected annual loss
• Social vulnerability
• County resilience

Starter code to generate the national map

# overall risk
output$county_risk <- renderText({
  # get selected county's overall risk score
  val <- selected_county() |>
    pull(national_risk_index_score_composite)

  # format using scales function
  label_number(accuracy = 1)(val)
})

Individual hazard percentiles

• Generate the county hazards dot plot and store in output$county_hazards.
• Incorporate appropriate validation checks for the inputs.

Starter code to generate the national map

Fill in the TODOs and correctly integrate into the server code chunk.

# get selected county's hazard percentiles
selected_county_hazards <- climate_risk |>
  filter(county == TODO)

# plot hazard percentiles
selected_county_hazards |>
  # reshape to long format for visualizing
  pivot_longer(
    cols = contains("hazard"),
    names_to = "hazard",
    values_to = "percentile"
  ) |>
  # only visualize selected hazard types
  filter(hazard %in% TODO) |>
  # order alphabetically
  mutate(hazard = str_remove(hazard, "_hazard_type_risk_index_score") |>
           make_clean_names(case = "title") |>
           fct_rev()) |>
  ggplot(mapping = aes(y = hazard)) +
  # all hazards range between 0 and 100
  geom_linerange(mapping = aes(xmin = 0, xmax = 100)) +
  # draw specific county
  geom_point(
    mapping = aes(x = percentile, color = percentile),
    size = 4
  ) +
  # optimized color palette
  scale_color_continuous_diverging(mid = 50, rev = TRUE, guide = "none") +
  # appropriate labels
  labs(
    x = "Percentile",
    y = NULL
  ) +
  # clean up the theme
  theme_minimal(base_size = 18) +
  theme(
    panel.grid.minor = element_blank(),
    panel.grid.major.y = element_blank()
  )