usrLonLat {oce}

Calculate Geographic Coordinates of Plot Box

Description

Trace along the plot box, converting from xy coordinates to lonlat coordinates. The results are used by mapGrid() and mapAxis() to ignore out-of-frame grid lines and axis labels.

Usage

usrLonLat(n = 25, debug = getOption("oceDebug"))

Arguments

n

number of points to check along each side of the plot box

debug

an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many oce functions. Generally, setting debug=0 turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value of debug first, so that a user can often obtain deeper debugging by specifying higher debug values.

Details

Some projections, such as "wintri", have trouble inverting points that are "off the globe". In such cases, the returned value has lonmin, lonmax, latmin and latmax set to NA, and ok set to FALSE.

Value

A list containing numerical values lonmin, lonmax, latmin, and latmax, along with logical value ok. The last of these indicates whether at least one point on the plot box is invertible. Note that longitudes are in the range from -180 to 180 degrees.

Author(s)

Dan Kelley

See Also

Other functions related to maps: formatPosition(), lonlat2map(), lonlat2utm(), map2lonlat(), mapArrows(), mapAxis(), mapContour(), mapCoordinateSystem(), mapDirectionField(), mapGrid(), mapImage(), mapLines(), mapLocator(), mapLongitudeLatitudeXY(), mapPlot(), mapPoints(), mapPolygon(), mapScalebar(), mapText(), mapTissot(), oceCRS(), shiftLongitude(), utm2lonlat()