Thank you for pointing to this possibility, I'll add it to the stars
docs somewhere.
This works but only slightly adapted, e.g. as
out = read_stars(system.file("tif/L7_ETMs.tif", package = "stars")) %>%
slice(band, 1) %>%
setNames("x") %>%
mutate(x = case_when (x<100 ~ NA_real_, x>100 & x<150 ~ 2))
where:
- I uses setNames("x") so that the attribute is renamed to "x", and you
can use x in the case_when expressions (rather than the lengthy
"L7_ETMs.tif")
- I chnaged NA into NA_real_ : the first RHS of the formulas need to be
all of the same type; as typeof(NA) is "logical", it breaks on the
second RHS which returns a numeric; if you would TRUE or FALSE rather
than 2 in the second case_when formula, using NA would be the right
thing to do in the first.
The examples of case_when document the need for typed NA in RHS: this is
intended behavior.
On 9/14/20 4:39 PM, Julian M. Burgos wrote:
Dear list,
I am wondering if there is a way to use logical statements to replace values of a stars
object, for example the case_when function or some other "tidyverse friendly"
approach. For example, I can do something like this:
st1 <- read_stars(system.file("tif/L7_ETMs.tif", package = "stars")) %>%
slice(band, 1)
st1[st1 < 100] <- NA
st1[st1 > 100 & st1 < 150] <- 2
... and so for. But I am wondering if there is a way to do this as part of a
pipe, looking something like this:
st1 <- read_stars(system.file("tif/L7_ETMs.tif", package = "stars")) %>%
slice(band, 1) %>%
mutate(x <- case_when (x<100 ~ NA,
x>100 & x<150 ~ 2))
Any ideas?
Takk,
Julian
--
Julian Mariano Burgos, PhD
Hafrannsóknastofnun, rannsókna- og ráðgjafarstofnun hafs og vatna/
Marine and Freshwater Research Institute
Botnsjávarsviðs / Demersal Division
Fornubúðir 5, IS-220 Hafnarfjörður, Iceland
www.hafogvatn.is
Sími/Telephone : +354-5752037
Netfang/Email: julian.bur...@hafogvatn.is
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Edzer Pebesma
Institute for Geoinformatics
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