---
title: "Adding annotations"
author: "Martin R. Smith"
date: "`r Sys.Date()`"
output: rmarkdown::html_document

vignette: >
  %\VignetteIndexEntry{Adding annotations}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

> Before you start, have you read the [introduction to the
Ternary package](Ternary.html)?

This vignette explores how to annotate specific points within a ternary plot.
We'll start by generating some example data:

```{r init}
set.seed(40) # For reproducibility

nPoints <- 40
points <- data.frame(a = abs(rnorm(nPoints, 2, 3)),
                     b = abs(rnorm(nPoints, 1, 1.5)),
                     c = abs(rnorm(nPoints, 1, 0.5)),
                     col = sample(2:5, nPoints, replace = TRUE),
                     label = paste("Point", seq_len(nPoints))
                     )

```

After plotting our data on a Ternary plot, we'll need to select which points to
annotate and where to place their labels.

```{r plot}
library("Ternary")

# Create ternary plot
par(mar = rep(0.2, 4)) # Set figure margins
TernaryPlot("a", "b", "c")

# Add points
TernaryPoints(points[, 1:3], col = points[, "col"], pch = 16)

# Choose points to label
toLabel <- c(10, 20, 30, 40)

# Get Cartesian coordinates of points
# Note that we need to rotate the data.frame with `t()`
pointXY <- TernaryToXY(t(points[toLabel, c("a", "b", "c")]))

# We will manually specify where we want to position our labels.
# It can help to establish the coordinates of the figure region:
par("usr") # c(x1, x2, y1, y2)

# And the X and Y range of the ternary plot itself:
TernaryXRange()
TernaryYRange()

# Manually select locations for labels:
labelXY <- rbind(c(0.28, 0.7),
                 c(0.35, 0.6),
                 c(0.42, 0.5),
                 c(0.49, 0.4))[c(3, 4, 1, 2), ]

# Add labels to plot
text(labelXY,
     labels = points[toLabel, "label"],
     col = points[toLabel, "col"],
     pos = 4, # Place text to right of coordinate
     xpd = NA # Don't clip at figure limit
     )

# Connect labels to points
segments(
  pointXY["x", ], pointXY["y", ],
  labelXY[, 1], labelXY[, 2],
  lwd = 2, # Line width
  col = points[toLabel, "col"]
)

```


# Where next

For other examples of usage, see the accompanying vignettes:

- [Introduction for new R users](new-users.html)

- [Getting started guide](Ternary.html)

- [Interpolating and contouring](interpolation.html)

- [Plotting Holdridge climate zones](Holdridge.html)
