GETXprofile {GEOmap} | R Documentation |
Cross sectional profile through a digital elevation map
Description
Example of how to use RPMG button functions. This example shows how to plot a DEM and interactively change the plot and find projected cross-sections through a surface.
Usage
GETXprofile(jx, jy, jz, LAB = "A", myloc = NULL, PLOT = FALSE, NEWDEV=TRUE, asp=1)
Arguments
jx , jy |
locations of grid lines at which the values in 'jz' are measured. |
jz |
a matrix containing the values to be plotted |
LAB |
Alphanumeric (A-Z) for labeling a cross section |
myloc |
Out put of Locator function |
PLOT |
logical. Plot is created if TRUE |
NEWDEV |
logical. Plot is on a new device if TRUE |
asp |
aspect ration for plotting, see par |
Details
The program uses a similar input format as image or contour, with structure from the locator() function of x and y coordinates that determine where the cross section is to be extracted.
Value
Returns a list of x,z values representing the projected values along the cross section.
RX |
distance along cross section |
RZ |
values extracted from the elevation map |
Note
The program is an auxiliary program provided to illustrate the RPMG interactive R analysis.
Author(s)
Jonathan M. Lees<jonathan.lees@unc.edu>
See Also
locator, image
Examples
## Not run:
####### get data
data(volcano)
#### extract dimensions of image
nx = dim(volcano)[1]
ny = dim(volcano)[2]
### establish units of image
jx = 10*seq(from=0, to=nx-1)
jy = 10*seq(from=0, to=ny-1)
#### set a letter for the cross section
LAB = LETTERS[1]
### coordinates of cross section on image
### this is normally set by using the locator() function
x1 = 76.47351
y1 = 231.89055
x2 = 739.99746
y2 = 464.08185
## extract and plot cross section
GETXprofile(jx, jy, volcano, myloc=list(x=c(x1, x2), y=c(y1, y2)), LAB=LAB, PLOT=TRUE)
## End(Not run)