Hi Robert
Thanks for your reply!
Your suggestion solved the problem, because in my case I do have cells where
there is NA in all layers.
But, I'm still a little puzzled about why it is not running in the case
where there is NA in a cell in only one of the layers.
lm() normally works in a case like this, so I am not sure why it is
returning an error here?
require(raster)
# From help to calc function
# create data
r <- raster(nrow=10, ncol=10)
s1 <- s2<- list()
for (i in 1:12) { s1[i] <- setValues(r, rnorm(ncell(r), i, 3) )
s2[i] <- setValues(r, rnorm(ncell(r), i, 3) )}
s1 <- stack(s1)
s2 <- stack(s2)
s <- stack(s1, s2)
r <- setValues(r, rnorm(ncell(r), 1, 3) )
plot(r)
r[1] <- NA #Setting top left corner to NA
plot(r)
s <- stack(s, r) # Now only one of the rasters has a NA value
# So this is equivalent to doing a lm with one NA value:
a <- rnorm(10, 5, 2)
b <- c(1:9, NA)
lm(a~b) # This seem to work ok.
# But with the brick:
fun <- function(x) { lm(x ~ time)$coefficients[2] }
time <- nlayers(s)
x5 <- calc(s, fun) # Error in model.frame.default(formula = x ~ time,
drop.unused.levels = TRUE) : variable lengths differ (found for 'time')
Best regards
Lars
Lars Dalby
Msc. PhD student
Ecoinformatics & Biodiversity
Department of Bioscience, Aarhus University
Denmark
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