plot_field_discrete: Plot a gridded field using discrete scale

In matteodefelice/panas: Reduce the friction when working with maps & time-series

Description

This function tries to produce high-quality maps of gridded fields using a discrete color-scale. The function is based on ggplot2. World borders will be used with the plot.

Usage

plot_field_discrete(x, lon, lat, lonlim = "auto", latlim = "auto",
  breaks = c(), labels = c(), color_scale = "Spectral",
  rev_color_scale = F, show_lat_lon_labels = T, varname = "x",
  mask = NULL, siglev = NULL, plot_only_sig = F, smooth = F,
  smooth_factor = 5, smooth_theta = 0.5, line_width = 0.5,
  dot_size = 0.5, grid_step = 10, font_size = 18,
  show_legend = TRUE)

Arguments

x	The field to be plotted, it can be both a matrix or a vector. See Details for more information.
lon	Vector of longitude values. Longitude should be in the range c(-180, 180), otherwise it will be transformed
lat	Vector of latitude values
lonlim	A vector of two values defining the longitude limits for the plot. The default is 'auto': it tries to detect the extreme directly from the provided longitude values.
latlim	A vector of two values defining the latitude limits for the plot. The default is 'auto': it tries to detect the extreme directly from the provided latitude values.
breaks	The vector to be used to define the color scale. If the vector contains N values (n_1, n_2, ..., n_k), the scale will have N+1 intervals: "<n_1", "n_1, n_2", ..., ">n_k". If breaks are not defined they are automatically computed diving the range of the plotted field in 5 intervals.
labels	A character vector containing all the labels associated to the breaks, the labels' lenght should have N+1 length with N the breaks' length
color_scale	This parameter defines the color palette. It might be a string defining the name of a colorbrewer (see colorbrewer2.org) palette or a list of all the colors associated to each interval.
rev_color_scale	logical value to define if the color_scale should be used reversed
show_lat_lon_labels	logical value that defines if labels for longitude and latitude should be shown
varname	Name of the plotted variable that appears on the legend bar
mask	Field of the same size of x that will be used to mask the values according to the parameter siglev (usually used to indicate statistical significance)
siglev	Scalar value that is used with mask to "mask" the values. All the points where mask <= siglev will be considered "significant" and then marked with dots (if plot_only_sig is FALSE)
plot_only_sig	If TRUE only the significant points will be plotted, otherwise the significance will be indicated with dots
smooth	Logical value that defines if a smoothing will be applied to the field
smooth_factor	The amplitude of the smoothing, the value indicates the "multiplication factor", i.e. how many points are used for each original grid points
line_width	Line width used for the plot
dot_size	Size of the dots used to indicate the significance
grid_step	Interval used for the lat-lon grid
font_size	Size of the fonts used in the plot
show_legend	Logical value to define if the colorbar should be visible
theta	This is the theta parameter of the function image.smooth from the fields package used for smoothing

Details

Details The field x should be or a matrix/array with 2 dimensions (consistent with lat and lon) or a vector. In the latter, it should have the same length of lat and lon to have a list of grid points. The returned ggplot object can be then combined with other ggplot layers, including coord* layers. We do not suggest to use projections because they are not well implemented with raster/tiles like in this case, especially when the latitude range is very close to the poles. To have a good representation of the field we suggest to add the layer coord_equal() or coord_quickmap() Comments about smoothing, description of the procedure.

Value

A ggplot object

matteodefelice/panas documentation built on March 4, 2020, 4:19 a.m.