Editing all raster cell values above a certain value in R

Question

I am using a bathymetric map of the Arctic Ocean containing 11617*11617 cells, each with a value for height relative to sea level (from -5573 to 5921 m). I wish to edit all pixels with values greater than 0 m to have a value of negative 10 m, and then save this raster.

bath=raster ('C:/Users/ls15g11/Desktop/IBCAO_V3_500m_RR_editinR.grd')
bath

class       : RasterLayer 
dimensions  : 11617, 11617, 134954689  (nrow, ncol, ncell)
resolution  : 500, 500  (x, y)
extent      : -2904250, 2904250, -2904250, 2904250  (xmin, xmax, ymin, ymax)
coord. ref. : NA 
data source : C:\Users\ls15g11\Desktop\IBCAO_V3_500m_RR_editinR.grd 
names       : z 
zvar        : z

I am very inexperienced with R, so would greatly appreciate any help on a way to achieve this.

score 8 · Accepted Answer · edited May 23 '17 at 12:08

8

First, let's create some dummy data as a 10x10 raster (to make this a reproducible example)

bath <- raster(nrows=10, ncols=10, vals=rnorm(100))

then we can simply do

bath[bath>0] <- -10

edited May 23 '17 at 12:08

Community

1
1

answered Jul 05 '16 at 19:08

dww

28,320
5
57
99

score 4 · Answer 2 · answered Jul 05 '16 at 23:44

4

Here is a memory-safe variation on dww's answer:

bath <- raster(nrows=10, ncols=10, vals=rnorm(100))

rbath <- reclassify(bath, cbind(0, Inf, -10), filename='file.grd')

answered Jul 05 '16 at 23:44

Robert Hijmans

31,122
4
43
51

Editing all raster cell values above a certain value in R

2 Answers2