Get started • ggpsychro

ggpsychro creates psychrometric charts with the same additive grammar used by ggplot2. Start with ggpsychro(), choose the chart limits and units, and then add grids, scales, stats, geoms, and themes with +.

ggpsychro(tdb_lim = c(0, 50), hum_lim = c(0, 30))

Default psychrometric chart with dry-bulb temperature and humidity ratio axes.

Chart limits and units

tdb_lim controls the dry-bulb temperature range. hum_lim controls the displayed humidity ratio range. SI units are used by default.

ggpsychro(tdb_lim = c(10, 35), hum_lim = c(0, 25), units = "SI")

SI psychrometric chart limited to 10 to 35 degrees C and 0 to 25 g per kg humidity ratio.

Use units = "IP" for IP charts. The dry-bulb limits are in degree F and the humidity-ratio limits are in grains per pound of dry air.

ggpsychro(tdb_lim = c(32, 122), hum_lim = c(0, 220), units = "IP")

IP psychrometric chart limited to 32 to 122 degrees F and 0 to 220 grains per pound humidity ratio.

Mollier charts

Set mollier = TRUE to swap the chart into Mollier orientation.

ggpsychro(tdb_lim = c(0, 50), hum_lim = c(0, 30), mollier = TRUE)

Mollier chart with humidity ratio on the x axis and dry-bulb temperature on the y axis.

Explicit coordinates

ggpsychro() sets up the psychrometric coordinate system for you. If you are building up a plot in smaller pieces, coord_psychro() can also be added explicitly.

ggpsychro() +
    coord_psychro(tdb_lim = c(10, 35), hum_lim = c(0, 25), units = "SI")

Psychrometric chart created by adding coord_psychro explicitly.

Add ggplot layers

Because the result is a ggplot object, regular ggplot layers work as usual.

states <- data.frame(
    dry_bulb_temperature = c(18, 23, 28, 31),
    humidity_ratio = c(8, 9.5, 10.5, 13)
)

ggpsychro(states, aes(dry_bulb_temperature, humidity_ratio),
    tdb_lim = c(0, 40), hum_lim = c(0, 25)
) +
    psychro_preset("minimal") +
    geom_point(color = "#0f766e", size = 2)

Minimal psychrometric chart with four state points added as a scatter layer.

For data recorded as relative humidity, wet-bulb temperature, vapor pressure, specific volume, or enthalpy, see Plotting psychrometric data.