vectorField: Vector field plot

In simulariatools: Simularia Tools for the Analysis of Air Pollution Data

Vector field plot

Description

Simple function to plot a vector field given two components.

Usage

vectorField(
  data,
  scale = 1,
  everyx = 1,
  everyy = 1,
  size = 0.25,
  preview = TRUE
)

Arguments

data	A dataframe containing data to be plotted in the form of: (x, y, u, v).
scale	length factor of vector components
everyx	keep one out of every everyx values, along x direction.
everyy	keep one out of every everyy values, along y direction.
size	arrow size.
preview	(default = TRUE) create a plot. If FALSE it only creates the ggplot2 directive to be added to another plot.

Details

This function plots a vector field given a data.frame with coordinates (x, y) and corresponding velocity components (u, v). Vectors are coloured by magnitude (speed). The coordinates are assumed to be on a regular rectangular grid in the UTM reference system.

This function is heavily inspired by snippets of code in R Graphics Cookbook by Winston Chang (https://r-graphics.org/index.html).

Value

A ggplot2 object if preview = TRUE. A ggplot2 a plot, as a contourPlot2() and the vector field will be overlapped.

Examples

## Not run: 
metU <- importADSOBIN(
    "/path/to/meteofile",
    variable = 'U',
    slice = 2,
    k = 1000,
    verbose = TRUE
)
metU <- as.data.frame(metU)
metU <- metU %>%
    mutate(u = z, z = NULL)

metV <- importADSOBIN(
    "/path/to/meteofile",
    variable = 'V',
    slice = 2,
    k = 1000,
    verbose = TRUE
 )
metV <- as.data.frame(metV)
metV <- metV |>
    mutate(v = z, z = NULL)

met <- merge(metU, metV, by = c("x", "y"))

vectorField(
    met,
    everyx = 2,
    everyy = 2,
    scale = 10
) +
    coord_fixed(ratio = 1, xlim = c(0, 1000), ylim = c(0, 1000)) +
    scale_color_viridis_c()

# Overlap the vector field to a contour plot and set vector colours to black
met$ws <- sqrt(met$u^2 + met$v^2)
contourPlot2(met, z = "ws") +
    vectorField(
        met,
        everyx = 2,
        everyy = 2,
        scale = 10,
        preview = FALSE
    ) +
    scale_colour_gradient(low = "black", high = "black", guide = NULL)

## End(Not run)

simulariatools documentation built on Sept. 1, 2025, 5:09 p.m.