read_envi {ursa} | R Documentation |
Read ENVI .hdr Labelled Raster file to memory
Description
Reads all or several bands of ENVI .hdr Labelled Raster file from disk to memory.
Usage
read_envi(fname, ...)
Arguments
fname |
Character. Filename for ENVI .hdr Labelled Raster file.
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... |
For read_envi : Set of arguments, which are recognized via their names (using regular expressions) and classes. In the case of grids mismatch some arguments (e.g., resample ) are passed to regrid function.
(subset)* Name can be omitted. Integer or character. If integer, then indices of bands, either positive or negative. Positive indices are for included bands, negative indices for omitted bands. If character, then either sequence of band names or regex string. By default (subset=NULL ), function reads all bands.
(ref)* Name can be omitted. ursaRaster or ursaGrid object. Reference grid for raster image resizing. By default (ref=NULL ) there is no resizing.
(nodata|ignorevalue) Numeric. Value, which is ignored. By default (nodata=NaN ) igrore value is taken from ENVI metadata (*.hdr or *.aux.xml).
reset(Grid)* Logical. If TRUE , then session grid is ignored, and new session grid is assigned from input file. If FALSE , then input file is nested in the session grid.
cache Integer. Using cache for compressed files. 0L - do not use cache, 1L - use cache; any other value resets cache. Default is FALSE .
verb(ose)* Logical. Value TRUE may provide some additional information on console. Default is FALSE .
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Details
Function read_envi
is designed to one-time reading (from disk to memory) ENVI .hdr Labelled Raster file. For multiple access to disk (by chunks), use followed construction:
a <- open_envi(fname)
d1 <- a[condition_1]
d2 <- a[condition_2]
...
close(a)
In this case, the connection keeps open. The gain is more effective for compressed binary files.
Value
Object of class ursaRaster
.
Author(s)
Nikita Platonov platonov@sevin.ru
See Also
open_envi
, Extract method [
for ursaRaster
object, close_envi
.
read_gdal
uses GDAL (rgdal) to read ENVI .hdr Labelled Raster file.
Examples
session_grid(NULL)
fname <- tempfile()
a <- ursa_dummy()
bandname(a) <- c("first","second","third")
write_envi(a,fname,compress=FALSE)
print(read_envi(fname))
print(read_envi(fname,c(1,3)))
print(read_envi(fname,-c(1,3)))
print(read_envi(fname,c("first","third")))
print(read_envi(fname,"iR"))
print(session_grid())
g <- regrid(session_grid(),mul=1/2.3)
b <- read_envi(fname,ref=g)
print(session_grid())
print(b)
envi_remove(fname)
[Package
ursa version 3.11.1
Index]