Hi Alessandro,
SAGA has a grid_calculus library. RSAGA provides a wrapper function
rsaga.grid.calculus, and even rsaga.linear.combination as a more
convenient version when you want to apply linear models to stacks of
grids. See ?rsaga.grid.calculus, there's also some example code.
Here some code for your problem of subtracting grids. I am playing
around with two small identical grids temp1.sgrd and temp2.sgrd and want
to show that their difference is zero.
library(RSAGA)
rsaga.grid.calculus(in.grids = c("temp1","temp2"),
out.grid = "result", formula = ~a-b)
# formula could also be formula = "a+b"
# 'a' refers to the first grid from in.grids,
# 'b' to the second one, etc.
# Same result:
#rsaga.linear.combination( c("temp1", "temp2"), "result",
# coef = c(1,-1))
# Let's have a look at the data in R
# (if the grid is not too large...):
rsaga.sgrd.to.esri("result", prec = 1)
res = read.ascii.grid("result", return.header = FALSE)
summary(as.vector(res)) # in my case, all ==0 because temp1=temp2
Note that there's also a wrapper function rsaga.close.gaps for the
module that you are using in the following piece of code:
> # filter the missing values using neighbours:
>
> rsaga.geoprocessor(lib="grid_tools", module=7,
> param=list(INPUT="DEM_1.sgrd", RESULT="DEM_1_f.sgrd", THRESHOLD=0.1))
I hope this helps.
Alex
Alessandro wrote:
Hi All,
I need help to write a code in R to subtract two raster in SAGA.
I have "DEM_1_f.sgrd" and "DSM_1_f.sgrd" in SAGA format and I wish to
subtract (DSM_1_f.sgrd - DEM_1_f.sgrd) to obtain a new layer
A part of the code is this:
#A# DEM - 1) Shapes to Grid
rsaga.get.usage("grid_gridding", 3)
rsaga.geoprocessor(lib="grid_gridding", module=3,
param=list(GRID="DEM_1.sgrd", INPUT="ground.shp", FIELD=0, LINE_TYPE=0,
USER_CELL_SIZE=dem.pixelsize, [EMAIL PROTECTED],1],
[EMAIL PROTECTED],2], [EMAIL PROTECTED],1],
[EMAIL PROTECTED],2]))
# filter the missing values using neighbours:
rsaga.geoprocessor(lib="grid_tools", module=7,
param=list(INPUT="DEM_1.sgrd", RESULT="DEM_1_f.sgrd", THRESHOLD=0.1))
#A# DSM - 2) Shapes to Grid
rsaga.get.usage("grid_gridding", 3)
rsaga.geoprocessor(lib="grid_gridding", module=3,
param=list(GRID="DSM_1.sgrd", INPUT="vegetation.shp", FIELD=0, LINE_TYPE=0,
USER_CELL_SIZE=dem.pixelsize, [EMAIL PROTECTED],1],
[EMAIL PROTECTED],2],
[EMAIL PROTECTED],1],
[EMAIL PROTECTED],2]))
# filter the missing values using neighbours:
rsaga.geoprocessor(lib="grid_tools", module=7,
param=list(INPUT="DSM_1.sgrd", RESULT="DSM_1_f.sgrd", THRESHOLD=0.1))
#DCM = DSM - DEM
Rsaga.geoprocessor(???)
Thanks for help
Ale
PS: is there a link with a SAGA and R codes banks
[[alternative HTML version deleted]]
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
--
Alexander Brenning
[EMAIL PROTECTED] - T +1-519-888-4567 ext 35783
Department of Geography and Environmental Management
University of Waterloo
200 University Ave. W - Waterloo, ON - Canada N2L 3G1
http://www.fes.uwaterloo.ca/geography/faculty/brenning/
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
