Substitute values in a Raster* object
Substitute (replace) values in a Raster* object with values in a data.frame. The data.frame should have a column to identify the key (ID) to match with the cell values of the Raster* object, and one or more columns with replacement values. By default these are the first and second column but you can specify other columns with arguments by and which. It is possible to match one table to multiple layers, or to use multiple layers as a single key, but not both.
## S4 method for signature 'Raster,data.frame' subs(x, y, by=1, which=2, subsWithNA=TRUE, filename='', ...)
x |
Raster* object |
y |
data.frame |
by |
column number(s) or name(s) identifying the key (ID) to match rows in data.frame |
which |
column number or name that has the new (replacement) values |
subsWithNA |
logical. If |
filename |
character. Optional output filename |
... |
additional arguments as for |
You could obtain the same result with reclassify, but subs is more efficient for simple replacement. Use reclassify if you want to replace ranges of values with new values.
You can also replace values using a fitted model. E.g. fit a model to glm or loess and then call predict
Raster object
r <- raster(ncol=10, nrow=10)
values(r) <- round(runif(ncell(r)) * 10)
df <- data.frame(id=2:8, v=c(10,10,11,11,12:14))
x <- subs(r, df)
x2 <- subs(r, df, subsWithNA=FALSE)
df$v2 <- df$v * 10
x3 <- subs(r, df, which=2:3)
s <- stack(r, r*3)
names(s) <- c('first', 'second')
x4 <- subs(s, df)
x5 <- subs(s, df, which=2:3)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.