I have 1 raster which I am resampling it multiple times (15 times). Each time I resample it, I am saving the result using as a name the name of the raster and some factor (see the code below). For example, if my raster's name is r, the output, after I resample it using a std of 0.2, should be r2. If the std is 0.25, the output should be r25 and so on. So far, I am doing this resampling manually but I would like to automate the process. Here is an example:
library(raster)
r = raster("path/r1.tif")
m = as.matrix(r)
psf = down_sample_image(m,
factor = 4.66,
gaussian_blur = T,
gauss_sigma = 0.2 * 450) # 0.2 to 0.9 with step 0.05
e <- extent(r)
m2r = raster(psf)
extent(m2r) <- e
plot(m2r)
raster::crs(m2r) <- "EPSG:7767"
writeRaster(m2r, "path/r2.tif")
The output name of the raster is determined based on the function gauss_sigma. So in the end, I should get the following rasters: r2, r25, r3, r35, r4, r45......r9. All in all, I am looking for a repeated process that: reads the same raster and performs the above analysis 15 times (only the value of gauss_sigma is changing from 0.2 to 0.9 with step 0.05. The *450 should stay the same). At every iteration, the output should be saved with a name based on the gauss_sigma value.
Here is my attempt (based on the answer below):
library(terra)
library(OpenImageR)
setwd("C:/Users/Geography/Desktop/multipolygon_test")
fname <- file.path(tempdir(), "a.tif")
r <- rast(ext(583400, 594200, 1005800, 1025900), res = 100, crs = "EPSG:7767")
values(r) <- sample(46:550, ncell(r), replace = T)
writeRaster(r, fname, overwrite = T)
dsi <- function(m, f) {
down_sample_image(m,
factor = 4.66,
gaussian_blur = T,
gauss_sigma = 0.20 * 450)
return(m / f)
}
ff <- c(0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90)
outf <- paste0(gsub("\\.tif$", "", fname), "_", 1:15, ".tif")
nms <- paste0("f_", ff)
m <- as.matrix(r)
for (i in seq_along(ff)) {
d <- dsi(m, ff[i])
m2r <- setValues(r, d)
writeRaster(m2r, outf[i], overwrite=TRUE, names=nms[i])
}
rast(outf)
Here is the output:
class : SpatRaster
dimensions : 201, 108, 15 (nrow, ncol, nlyr)
resolution : 100, 100 (x, y)
extent : 583400, 594200, 1005800, 1025900 (xmin, xmax, ymin, ymax)
coord. ref. : WGS 84 / Maharashtra (EPSG:7767)
sources : a_1.tif
a_2.tif
a_3.tif
... and 12 more source(s)
names : f_0.2, f_0.25, f_0.3, f_0.35, f_0.4, f_0.45, ...
min values : 230, 184, 153.3333, 131.4286, 115, 102.2222, ...
max values : 2750, 2200, 1833.3334, 1571.4286, 1375, 1222.2222, ...
The issue is I don't know how to export those raster files. I tried using the writeRaster function but I am getting this error (one of my many tries):
Error in (function (classes, fdef, mtable) :
unable to find an inherited method for function ‘writeRaster’ for signature ‘"character", "character"’
Any ideas why that might be?
Here is a small raster:
r = raster(extent(583400, 594200, 1005800, 1025900), res=100, crs="EPSG:7767")
values(r) <- sample(46:550, ncell(r), replace=T)
Here is what I did, based on the answer above:
library(gridkernel)
library(gridprocess)
library(raster)
tirs = raster("path/tirs.tif")
cr = raster("path/ntl.tif")
for (i in seq(from = 0.2, to = 0.9, by = 0.05)) {
g = as.grid(tirs)
smoothed = gaussiansmooth(g, sd = i * 460, max.r = 100)
r <- raster(smoothed)
raster::crs(r) <- "EPSG:7755"
print(i)
r = resample(r, cr, method = "ngb")
stringedi = gsub("0\\.", "", toString(format(i, nsmall = 2)))
file_name <- paste0("tirs", stringedi, ".txt")
print(file_name)
# Make sure here you supply full path to folder without the last "/"
full_file_path = paste0("path", "/", file_name)
writeRaster(r, full_file_path, format = "GTiff", overwrite = T)
}