stars objects and case_when

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

stars objects and case_when

Julian M. Burgos
CONTENTS DELETED
The author has deleted this message.
Reply | Threaded
Open this post in threaded view
|

Re: stars objects and case_when

edzer
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: [hidden email]
>
> _______________________________________________
> R-sig-Geo mailing list
> [hidden email]
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

--
Edzer Pebesma
Institute for Geoinformatics
Heisenbergstrasse 2, 48149 Muenster, Germany
Phone: +49 251 8333081

_______________________________________________
R-sig-Geo mailing list
[hidden email]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Reply | Threaded
Open this post in threaded view
|

Re: stars objects and case_when

Julian M. Burgos
CONTENTS DELETED
The author has deleted this message.