geodensityplot

Geographic density plot

Syntax

geodensityplot(lat,lon)

geodensityplot(lat,lon,weights)

geodensityplot(___,Name,Value)

geodensityplot(gx,___)

dp = geodensityplot(___)

Description

geodensityplot(lat,lon) creates a density plot in a geographic axes from locations specified (in degrees) by the coordinate vectors lat and lon. lat and lon must be the same size.

geodensityplot(lat,lon,weights) specifies weights for the data points in weights.

geodensityplot(___,Name,Value) specifies DensityPlot properties using one or more Name,Value pair arguments.

geodensityplot(gx,___) plots in the geographic axes specified by gx instead of the current axes.

dp = geodensityplot(___) returns a DensityPlot object.

Examples

Create Geographic Density Plot

Set up latitude and longitude data.

lon = linspace(-170,170,3000) + 10*rand(1,3000);
lat = 50 * cosd(3*lon) + 10*rand(size(lon));

Specify weights for each data point.

weights = 101 + 100*(sind(2*lon));

Create the geographic density plot, specifying the colors used with the plot.

geodensityplot(lat,lon,weights,'FaceColor','interp')

Input Arguments

lat — Latitude coordinates of data points

real, numeric, finite vector within the range [-90 90]

Latitude coordinates of data points, specified as a real, numeric, finite vector in degrees, within the range [-90 90]. The vector can contain embedded NaNs. lat must be the same size as lon.

Example: [43.0327 38.8921 44.0435]

Data Types: single | double

lon — Longitude coordinates in degrees

real, numeric, finite vector

Longitude coordinates in degrees, specified as a real, numeric, finite vector. The vector can contain embedded NaNs. lon must be the same size as lat.

Longitudes must span less than (or equal to) 360 degrees.

Example: [-107.5556 -77.0269 -72.5565]

Data Types: single | double

weights — Weights assigned to data

[] (default) | scalar | numeric vector

Weights assigned to data, specified as an empty array, a scalar, or a numeric array. If you specify a numeric vector, the vector must be the same length as the lat and lon vectors. The weights vector is typically additional data you have related to the location data in lat and lon.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

gx — Target geographic axes

GeographicAxes object

Target geographic axes, specified as a GeographicAxes object.¹ You can modify the appearance and behavior of a GeographicAxes object by setting its properties. For a list of properties, see GeographicAxes Properties.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: dp = geodensityplot(lat,lon,weights,'FaceColor','g')

Note

The density plot properties listed here are frequently used properties. For a complete list, see DensityPlot Properties.

FaceAlpha — Face transparency

'interp' (default) | scalar in range [0,1]

Face transparency, specified as one of these values:

• Scalar in range [0,1] — Use uniform transparency across all the faces. A value of 1 is fully opaque and 0 is completely transparent. Values between 0 and 1 are semitransparent.

• 'interp' — Use interpolated transparency for each face. The transparency varies across each face by interpolating the values at the vertices. Transparency values are chosen from the parent axes alphamap.

FaceColor — Face color

[0 0.4470 0.7410] (default) | 'interp' | RGB triplet | hexadecimal color code | 'r' | 'g' | 'b' | ...

Face color, specified as 'interp', an RGB triplet, a hexadecimal color code, a color name, or a short name. The value 'interp' uses interpolated coloring based on density values, where colors are chosen from the colormap of the parent axes.

RGB triplets and hexadecimal color codes are useful for specifying custom colors.

• An RGB triplet is a three-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0,1]; for example, [0.4 0.6 0.7].

• A hexadecimal color code is a character vector or a string scalar that starts with a hash symbol (#) followed by three or six hexadecimal digits, which can range from 0 to F. The values are not case sensitive. Thus, the color codes "#FF8800", "#ff8800", "#F80", and "#f80" are equivalent.

Alternatively, you can specify some common colors by name. This table lists the named color options, the equivalent RGB triplets, and hexadecimal color codes.

Color Name	Short Name	RGB Triplet	Hexadecimal Color Code	Appearance
"red"	"r"	[1 0 0]	"#FF0000"
"green"	"g"	[0 1 0]	"#00FF00"
"blue"	"b"	[0 0 1]	"#0000FF"
"cyan"	"c"	[0 1 1]	"#00FFFF"
"magenta"	"m"	[1 0 1]	"#FF00FF"
"yellow"	"y"	[1 1 0]	"#FFFF00"
"black"	"k"	[0 0 0]	"#000000"
"white"	"w"	[1 1 1]	"#FFFFFF"

Here are the RGB triplets and hexadecimal color codes for the default colors MATLAB^® uses in many types of plots.

RGB Triplet	Hexadecimal Color Code	Appearance
[0 0.4470 0.7410]	"#0072BD"
[0.8500 0.3250 0.0980]	"#D95319"
[0.9290 0.6940 0.1250]	"#EDB120"
[0.4940 0.1840 0.5560]	"#7E2F8E"
[0.4660 0.6740 0.1880]	"#77AC30"
[0.3010 0.7450 0.9330]	"#4DBEEE"
[0.6350 0.0780 0.1840]	"#A2142F"

Radius — Radius of influence each point has on density calculation

numeric scalar

Radius of influence each point has on density calculation, specified as a numeric scalar. When used in a GeographicAxes, the value is measured in meters.

Output Arguments

dp — Geographic density plot

DensityPlot

Geographic density plot, returned as a DensityPlot object.

Tips

• To customize the geographic axes, modify geographic axes properties. For a list of properties, see GeographicAxes Properties.

• If you have Mapping Toolbox™, you can specify basemaps of your own choosing using the addCustomBasemap function.

• When you plot on geographic axes, the geodensityplot function assumes that coordinates are referenced to the WGS84 coordinate reference system. If you plot using coordinates that are referenced to a different coordinate reference system, then the coordinates may appear misaligned.

Version History

Introduced in R2018b

R2022b: Adding new plots to geographic axes does not reset basemap

When you plot into geographic axes by using functions such as geodensityplot and geoplot, MATLAB does not reset the basemap. In R2022a and earlier releases, the basemap resets when you add new plots.

As a result, you can specify a basemap and then visualize data without using the hold function between commands. For example, this code creates a map using the streets basemap. Then it displays a density plot over the basemap. In R2022b, the basemap does not reset. In R2022a and earlier releases, the basemap resets to the default streets-light.

load cycloneTracks;
lat = cycloneTracks.Latitude;
lon = cycloneTracks.Longitude;
 
figure
geobasemap streets
geodensityplot(lat,lon,"FaceColor","m")

This change does not affect existing code that sets the hold state to "on" between commands.

To reset the basemap when you add a new plot, use the cla reset syntax of the cla function before you create the plot. For example, to update the preceding code, use cla reset between the calls to geobasemap and geodensityplot.

load cycloneTracks;
lat = cycloneTracks.Latitude;
lon = cycloneTracks.Longitude;
 
figure
geobasemap streets
cla reset
geodensityplot(lat,lon,"FaceColor","m")

Alternatively, you can change the basemap to the default streets-light by using the geobasemap function. For more information about changing the basemap of geographic axes, see Access Basemaps for Geographic Axes and Charts.