在栅格立方体中与自定义 function 聚合

Question

I have raster data on daily temperatures, and I want to aggregate them to monthly 95th percentile. After some trying and research eg, help pages of terra::tapp or gdalcubes::aggregate_time I was not able to get monthly quantiles. Is there a way how to do that?

library(terra)
r <- rast( system.file("ex/elev.tif", package="terra") )
rast<-c(r,r,r,r)
time(rast)<-as.POSIXct(c("2023-01-16","2023-01-17","2023-01-18","2023-01-19"),tz="UTC")

# works as expected
rast2 <- tapp(rast, "months", max ) 

# does not work
rast2 <- tapp(rast, "months", fun = function(i) quantile(i, probs = 0.95, na.rm = T))

Answer 1

What do you mean with "does not work". You should at least add the error message you see, or explain why the results are not as expected.

I think it works fine. In the example data I use two months, otherwise it makes no sense to use tapp , you could just use app if there is only one month.

library(terra)
#terra 1.6.53
r <- rast( system.file("ex/elev.tif", package="terra") )
rast <- rep(r, 6) * 1:6
time(rast)<-as.POSIXct(c("2023-01-16","2023-01-17","2023-01-18","2023-02-17","2023-02-18","2023-02-19"),tz="UTC")

x <- tapp(rast, "months", max) 
y <- tapp(rast, "months", fun = function(i) quantile(i, probs = 0.95, na.rm = T))
y
#class       : SpatRaster 
#dimensions  : 90, 95, 2  (nrow, ncol, nlyr)
#resolution  : 0.008333333, 0.008333333  (x, y)
#extent      : 5.741667, 6.533333, 49.44167, 50.19167  (xmin, xmax, ymin, ymax)
#coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#source(s)   : memory
#names       :    m_1,    m_2 
#min values  :  408.9,  831.9 
#max values  : 1586.3, 3227.3 
#time (mnts) : Jan to Feb