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Plotting

Brock

2025-12-01

Source: vignettes/plotting.Rmd
plotting.Rmd

Plotting

Default Plot Method

Running the plot function on a trackframe creates a plot of the location points, joined by lines in temporal order, with easting on the x-axis and northing on the y-axis. By default, all tracks are plotted with an aspect ratio of 1, each in a different color. The start point of each track is marked by an arrowhead, and the end point of each track is marked by a bar.

##        x     y      id time
## 1  124.4 170.1 track_1    1
## 2  118.8 150.2 track_1    2
## 3  119.4 150.9 track_1    3
## 4  111.1 138.7 track_1    4
## 5   91.0 130.7 track_1    5
## 6   83.3 140.9 track_1    6
## 7   84.1 155.1 track_1    7
## 8  110.3 160.2 track_2    1
## 9  120.2 167.7 track_2    2
## 10 119.9 166.5 track_2    3
## 11 132.3 168.7 track_2    4
## 12 134.1 171.6 track_2    5
## 13 150.7 165.2 track_2    6
## 14 161.8 152.4 track_2    7
## 15 130.3 150.2 track_3    1
## 16 137.3 138.2 track_3    2
## 17 140.7 130.5 track_3    3
## 18 139.6 125.0 track_3    4
## 19 144.2 115.9 track_3    5
## 20 152.9  99.5 track_3    6
## 21 144.5 103.2 track_3    7
tf_demo <- as.trackframe(df_demo, crs = NA)
plot(tf_demo)

Customizing Default Plot Method

trackframe’s plotting functions are based on the tinyplot package (vignette("introduction", package = "tinyplot")). This means that it responds to largely the same parameters as base R plots, and that tinyplot’s syntax can be used.

Controling Visible Elements

Each element of the plot (lines, points, start indicators and end indicators) can be turned on and off.

For example, if you want to show lines only:

plot(tf_demo, points = FALSE, start_indicator = FALSE, end_indicator = FALSE)

Or points only:

plot(tf_demo, lines = FALSE, start_indicator = FALSE, end_indicator = FALSE)

Changing the Theme

You can also change the theme of the plot to any of tinyplot’s built-in and custom themes. For example:

tinyplot::tinytheme("dark")
plot(tf_demo)

tinyplot::tinytheme("tufte")
plot(tf_demo)

# Reset theme
tinyplot::tinytheme()

The full range of tinyplot themes is shown here: (vignette("themes", package = "tinyplot"))

Adjusting Styles

The style of individual elements can also be adjusted by passing parameters as a list to that element’s corresponding _style argument.

For example, if you want the points to be large, you can adjust the cex in a list of the points_style argument:

plot(tf_demo, points_style = list(cex = 3), start_indicator = FALSE, end_indicator = FALSE)

If you want to change the line thickness, you can change the lwd in a list of the lines_style argument:

plot(tf_demo, lines_style = list(lwd = 8), start_indicator = FALSE, end_indicator = FALSE)

These styling lists (and the plot() method itself) take parameters passable to tinyplot::tinyplot. This includes parameters defined in graphics::par …

plot(tf_demo, col = "blue")

… as well as parameters defined directly in tinyplot::tinyplot.

Parameters that apply to the entire plot, not just one element, can be passed directly to plot(...) rather than in a _style list.

plot(tf_demo, legend = FALSE)

Adjusting Indicators

The start and end indicators are arrows. Their style can be adjusted as well using parameters that apply to arrows.

For example, you can adjust the size of the arrowhead with the length parameter.

We can make the end indicators big and start indicators tiny:

plot(tf_demo, start_indicator_style = list(length = .05), end_indicator_style = list(length = 0.3))

You can also use the arrowhead_loc parameter to move the arrowhead away from the exact start/endpoint of each track toward the second/second-to-last point.

For example, this puts the start arrowhead 60% of the way between the first point of each track and the second point of each track, and puts the end arrowhead, 20% of the way between the last point in each track and the second-to-last point:

plot(
  tf_demo,
  start_indicator_style = list(arrowhead_loc = .6),
  end_indicator_style = list(arrowhead_loc = .2)
)

Plotting Markers

If you want to highlight certain non-endpoints, create an indicator column with the points you’d like to highlight marked as TRUE and all others marked as FALSE. Then, pass the name of the column to the plot() method as the marker arg.

# Create an indicator column, all points marked as FALSE
tf_demo$track_1_2nd_point <- FALSE

# Mark the 2nd element of track_1 as TRUE
tf_demo$track_1_2nd_point[id(tf_demo) == "track_1"][2] <- TRUE

plot(tf_demo, marker = "track_1_2nd_point")

By default, makers appear as boxes around the relevant datapoint. Similar to other elements, they can be styled with marker_style.

plot(tf_demo, marker = "track_1_2nd_point", marker_style = list(pch = "2", cex = 10))