Holdridge.R
In Ternary: Create Ternary and Holdridge Plots

## ----hcl-colors-hack, echo=FALSE----------------------------------------------
if (getRversion() < "3.6") {
  hcl.colors <- function(n, ...) {
    colorRampPalette(c("#4B0055", "#274983", "#008298", "#00B28A",
                         "#7ED357", "#FDE333"))(n)
  }
}

## ----holdridge, fig.asp = 1---------------------------------------------------
# Load package and data
library("Ternary")

data(holdridge, holdridgeLifeZonesUp, package = "Ternary")

# Suppress plot margins
par(mar = c(0, 0, 0, 0))

# Create blank Holdridge plot
HoldridgePlot(hex.labels = holdridgeLifeZonesUp)
HoldridgeBelts()

# Plot data, shaded by latitude
HoldridgePoints(holdridge$PET, holdridge$Precipitation,
                col = hcl.colors(91)[abs(holdridge$Latitude) + 1],
                lwd = 2)

# Add legend to interpret shading
PlotTools::SpectrumLegend(
  "topright", bty = "n", # No box
  horiz = TRUE, # Horizontal
  x.intersp = -0.5, # Squeeze in X direction
  legend = paste0(seq(0, 90, 15), "°"),
  palette = hcl.colors(91),
  title = "Latitude"
)