# GETXprofile: Cross sectional profile through a digital elevation map In GEOmap: Topographic and Geologic Mapping

## 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

 `1` ```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>

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26``` ```## Not run: ####### get data data(volcano) #### extract dimensions of image nx = dim(volcano) ny = dim(volcano) ### 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 ### 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) ```