stdm (Mapping Toolbox)

Compute standard deviation for geographic data

Syntax

[latdev,londev] = stdm(lat,lon)
[latdev,londev] = stdm(lat,lon,geoid)
[latdev,londev] = stdm(lat,lon,units)
[latdev,londev] = stdm(lat,lon,geoid,units)
geodevs = stdm(...)

Background

Determining the deviations of geographic data in latitude and longitude is more complicated than simple sum-of-squares deviations from the data averages. For latitude deviation, a straightforward angular standard deviation calculation is performed from the geographic mean as calculated by meanm. For longitudes, a similar calculation is performed based on data departure rather than on angular deviation. See the section entitled "Geographic Statistics" in the "Mapping Applications" chapter of the Mapping Toolbox User's Guide.

Description

[latdev,londev] = stdm(lat,lon) returns row vectors of the latitude and longitude geographic standard deviations for the data points specified by the columns of lat and lon.

[latdev,londev] = stdm(lat,lon,units) indicates the angular units of the data. When the standard angle string units is omitted, 'degrees' is assumed. Output measurements are in terms of these units (as arc length distance).

[latdev,londev] = stdm(lat,lon,geoid) specifies the elliptical definition of the Earth to be used with the two-element geoid vector. The default geoid model is a spherical Earth, which is sufficient for most applications. Output measurements are in terms of the distance units of the geoid vector.

If a single output argument is used, then geodevs = [latdev longdev]. This is particularly useful if the original lat and lon inputs are column vectors.

Examples

Create latitude and longitude matrices using the worldo dataset (compare with example for stdist):

load worldlo
lat=[PPpoint(2:5).lat]
lat =
    5.3386   24.5808    5.4619   36.8862
lon=[PPpoint(2:5).long]
lon =
   -3.7602   54.9619   -0.3450   35.5141
[latstd,lonstd]=stdm(lat,lon)
latstd =
    8.9962
lonstd =
  159.1153

See Also

departure
Departure of longitudes at specific latitudes

filterm
Geographic filter for data sets

hista
Spatial equal area histogram

histr
Spatial equirectangular histogram

meanm
Mean for geographic data

stdist
Standard distances for geographic data

`departure`	Departure of longitudes at specific latitudes
`filterm`	Geographic filter for data sets
`hista`	Spatial equal area histogram
`histr`	Spatial equirectangular histogram
`meanm`	Mean for geographic data
`stdist`	Standard distances for geographic data

stdist stem3m