R: Cross sectional profile through a digital elevation map

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)

[Package GEOmap version 2.4-0 Index]