Mapping Toolbox

stdm

Compute standard deviation for geographic data

Syntax

[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,ellipsoid) specifies the elliptical definition of the Earth to be used with the two-element ellipsoid vector. The default ellipsoid model is a spherical Earth, which is sufficient for most applications. Output measurements are in terms of the distance units of the ellipsoid vector.

[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).

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.

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 "Geographic Statistics" in the "Mapping Applications" chapter of the Mapping Toolbox User's Guide documentation.

Examples

Create latitude and longitude matrices using the worldlo data set (compare with the 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

stdist

stem3m