Mapping Toolbox™

stdm - Standard deviation for geographic points

Syntax

[latdev,londev] = stdm(lat,lon)
[latdev,londev] = stdm(lat,lon,ellipsoid)
[latdev,londev] = stdm(lat,lon,units)

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,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 Toolbox User's Guide.

Examples

Create latitude and longitude lists using the worldcities data set and obtain standard distance deviation for group (compare with the example for stdist):

cities = shaperead('worldcities.shp', 'UseGeoCoords', true);
Paris = strmatch('Paris',{cities(:).Name});
London = strmatch('London',{cities(:).Name});
Rome = strmatch('Rome',{cities(:).Name});
Madrid = strmatch('Madrid',{cities(:).Name});
Berlin = strmatch('Berlin',{cities(:).Name});
Athens = strmatch('Athens',{cities(:).Name});
lat = [cities(Paris).Lat cities(London).Lat...
       cities(Rome).Lat cities(Madrid).Lat...
       cities(Berlin).Lat cities(Athens).Lat]
lon = [cities(Paris).Lon cities(London).Lon...
       cities(Rome).Lon cities(Madrid).Lon...
       cities(Berlin).Lon cities(Athens).Lon]
[latstd,lonstd]=stdm(lat,lon)

lat =
   48.8708   51.5188   41.9260   40.4312   52.4257   38.0164
lon =
    2.4131   -0.1300   12.4951   -3.6788   13.0802   23.5183
latstd =
    2.7640
lonstd =
   68.7772

See Also

departure, filterm, hista, histr, meanm, stdist

stdist

stem3m