crop: Cut a satin object

In satin: Visualisation and Analysis of Ocean Data Derived from Satellites

Cut a satin object

Description

Select and cut a polygon shaped area of interest from a satin object.

Usage

crop(X, polygon = NULL, return.poly = FALSE)

Arguments

X	a satin object as returned by read.nasaoc, read.ghrsst, read.osunpp, or read.cmems.
polygon	a polygon defining the area of interest (aoi) to be cutted.
return.poly	if TRUE, crop returns a list with the cutted satin object and the polygon drawn (a data frame).

Details

If provided, the polygon defining the aoi must have two columns with x and y coordinates. The function verifies that the last point is exactly the same as the first one. When not specified, the user can draw a polygon by clicking on a previously displayed image. Note that for drawing the polygon in this manner, the plot of the satin object has to be created using colbar = FALSE. The result is a satin object where the pixels outside the aoi are set to NA. In order to cut Copernicus data returned from read.cmems, the appropriate indexing should be previously done.

Value

A cutted satin object.

When return.poly = TRUE, a list with two components:

aoi	cutted satin object.
polygon	polygon coordinates defining the aoi.

Author(s)

Héctor Villalobos

See Also

getpoly

Examples

# load and display sample data
data(dsst)
plot(dsst)
  
# define polygon, cut the image and display the aoi
polyg <- data.frame(x = c(-110, -105, -113, -116, -110), y = c(23, 23, 32, 32, 23))
dsst.clip <- crop(dsst, polygon = polyg)
plot(dsst.clip)

if(interactive()){ 
# the same, but polygon is defined by clicking on the image
plot(dsst, colbar = FALSE)
dsst.clip2 <- crop(dsst, return.poly = TRUE) # *** draw the aoi polygon ***
dsst.clip2$polygon # show polygon coordinates
plot(dsst.clip2$aoi) # plot the selected aoi
}

satin documentation built on Sept. 23, 2022, 1:06 a.m.