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I have an R Leaflet map showing cicles to mark the locations of industrial facilities. Some of these facilities have been assigned a risk score in the data ("RSEI_Score"), and others not (see working code below).

I have used an ifelse statement to assign a fixed radius to those without an RSEI score, and a square root function to make the radius of the remaining vary according to the score. Here is the line:

radius = ~ifelse(is.na(RSEI_Score), 300, sqrt(RSEI_Score) * 1.5),

However, some of the scores are very small, resulting in very small circles. I need to assign a minimum size of 300 to the circles that do have scores. I thought I could do that using "max" and setting a minimum, plus the sqrt value as maximum, but either I am doing it wrong, or it needs another technique. Does anyone know how to do it?

# Load libraries
library(leaflet)
library(sf)

# Read the CSV file
df <- read.csv("https://s3.us-east-2.amazonaws.com/ecotopia.today/Data/LA_TRI_RSEI_2021.csv")

# Convert WKT to sf geometry
df_sf <- st_as_sf(df, wkt = "WKT")

# Define color palette 
custom_palette <- colorRampPalette(c("#AF59BA", "#009ADE", "#F28522", "#FF1F5B"))

# Create Leaflet map with circles and color ramp
leaflet(df_sf) %>%
  addProviderTiles("Stadia.Outdoors") %>%
  addCircles(
    radius = ~ifelse(is.na(RSEI_Score), 300, sqrt(RSEI_Score) * 1.5),
    color = "black",
    weight = 1,
    fillColor = ~ifelse(is.na(RSEI_Score), "#FFC61E", custom_palette(length(unique(df$RSEI_Score)))[seq_along(unique(df$RSEI_Score))]),
    fillOpacity = 0.7,
    popup = ~paste(as.character(PRIMARY_NAME), "<br>Risk factor: ", ifelse(is.na(RSEI_Score), "N/A", RSEI_Score)),
    label = ~paste(as.character(PRIMARY_NAME))
  ) %>%
  setView(lng = -90.95599, lat = 30.098563, zoom = 10)

1 Answer 1

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In the end, I found two answers. First, the right way, using pmax and pmin:

# Define minimum and maximum sizes
min_size <- 5
max_size <- 40

# Set the radius with a minimum and maximum size
df_sf$radius <- ifelse(is.na(df_sf$RSEI_Score), min_size, sqrt(df_sf$RSEI_Score) * 0.02)
df_sf$radius <- pmax(min_size, pmin(df_sf$radius, max_size))

# use the radius value in addCirles options
radius = ~radius,

Next, the workaround whose effect I like better. It simply adds the minimum size of 300 to the square root values, ensuring that the points with values are always larger than those without:

    radius = ~ifelse(is.na(RSEI_Score), 300, 300 + sqrt(RSEI_Score) * 1.5),

I also realized I should be using markerCircles rather than just circles, but that's another story.

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