| Mapping Toolbox | |
Compute standard distance of geographic data
Syntax
dist = stdist(lat,lon) dist = stdist(lat,lon,units) dist = stdist(lat,lon,geoid) dist = stdist(lat,lon,geoid,units) dist = stdist(lat,lon,geoid,units,method)
Background
The command stdm provides independent standard deviations in latitude and longitude of data points. stdist provides a means of examining data scatter that does not separate these components. The result is a standard distance, which can be interpreted as a measure of the scatter in great circle distance of the data points from the centroid as returned by meanm.
Description
dist = stdist(lat,lon) returns a row vector of the latitude and longitude geographic standard distance for the data points specified by the columns of lat and lon.
dist = stdist(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).
dist = stdist(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.
dist = stdist(lat,lon,geoid,units,method) specifies the method of calculating the standard distance of the data. The default, 'linear', is simply the average great circle distance of the data points from the centroid. Using 'quadratic' results in the square root of the average of the squared distances, and 'cubic' results in the cube root of the average of the cubed distances.
The output distance can be thought of as the radius of a circle centered on the geographic mean position, which gives a measure of the spread of the data.
Examples
Generate latitude and longitude matrices using the worldo dataset (compare with example for stdm):
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 dist= stdist(lat,lon) dist = 26.5282
See Also
meanm |
Mean of geographic data |
stdm |
Standard deviation of geographic data |
| | spzerom | stdm | |