terra::predict() drops or changes layer names based on the value of index

[mikemahoney218]

Problem

The names returned by terra::predict() are partially dependent upon the value provided to index. My testing suggests that if index isn't provided, then any names returned by fun are used; if index is provided and the return has the same number of bands as the input raster, names of the input raster are used (even if that band wasn't used for calculations); and if index is longer than the number of input bands, the default lyr.1-type names are used.

I think ideally any names returned by fun would be preserved, irrespective of index.

reprex

library(terra)
#> terra 1.7.37

test <- rast(ncols = 1000, nrows = 1000, xmin=0)
values(test) <- rnorm(ncell(test))
names(test) <- "name_from_raster"

dummy_model <- list()

terra::predict(
  test, 
  dummy_model, 
  fun = function(object, newdata) { 
    return(data.frame(x = newdata[[1]] * 0.5))
  }
)
#> class       : SpatRaster 
#> dimensions  : 1000, 1000, 1  (nrow, ncol, nlyr)
#> resolution  : 0.18, 0.18  (x, y)
#> extent      : 0, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 
#> source(s)   : memory
#> name        :        x 
#> min value   : -2.53496 
#> max value   :  2.38629

terra::predict(
  test, 
  dummy_model, 
  fun = function(object, newdata) { 
    return(data.frame(x = newdata[[1]] * 0.5))
  },
  index = 1
)
#> class       : SpatRaster 
#> dimensions  : 1000, 1000, 1  (nrow, ncol, nlyr)
#> resolution  : 0.18, 0.18  (x, y)
#> extent      : 0, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 
#> source(s)   : memory
#> name        : name_from_raster 
#> min value   :         -2.53496 
#> max value   :          2.38629

terra::predict(
  test, 
  dummy_model, 
  fun = function(object, newdata) { 
    return(data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2))
  },
  index = 1:2
)
#> class       : SpatRaster 
#> dimensions  : 1000, 1000, 2  (nrow, ncol, nlyr)
#> resolution  : 0.18, 0.18  (x, y)
#> extent      : 0, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 
#> source(s)   : memory
#> names       :     lyr1,       lyr2 
#> min values  : -2.53496, -10.139838 
#> max values  :  2.38629,   9.545159

terra::predict(
  c(test, setNames(test, "another_name")), 
  dummy_model, 
  fun = function(object, newdata) { 
    return(data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2))
  },
  index = 1:2
)
#> class       : SpatRaster 
#> dimensions  : 1000, 1000, 2  (nrow, ncol, nlyr)
#> resolution  : 0.18, 0.18  (x, y)
#> extent      : 0, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 
#> source(s)   : memory
#> names       : name_from_raster, another_name 
#> min values  :         -2.53496,   -10.139838 
#> max values  :          2.38629,     9.545159

# `index` is documented as only accepting integers,
# so it's perhaps surprising this works at all
terra::predict(
  test, 
  dummy_model, 
  fun = function(object, newdata) { 
    return(data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2))
  },
  index = c("x", "y")
)
#> class       : SpatRaster 
#> dimensions  : 1000, 1000, 2  (nrow, ncol, nlyr)
#> resolution  : 0.18, 0.18  (x, y)
#> extent      : 0, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 
#> source(s)   : memory
#> names       :     lyr1,       lyr2 
#> min values  : -2.53496, -10.139838 
#> max values  :  2.38629,   9.545159

^{Created on 2023-06-21 with reprex v2.0.2}

Session info

sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value
#>  version  R version 4.3.0 (2023-04-21)
#>  os       Ubuntu 22.04.2 LTS
#>  system   x86_64, linux-gnu
#>  ui       X11
#>  language (EN)
#>  collate  en_US.UTF-8
#>  ctype    en_US.UTF-8
#>  tz       America/New_York
#>  date     2023-06-21
#>  pandoc   3.1.1 @ /usr/lib/rstudio/resources/app/bin/quarto/bin/tools/ (via rmarkdown)
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package     * version date (UTC) lib source
#>  cli           3.6.1   2023-03-23 [1] CRAN (R 4.3.0)
#>  codetools     0.2-19  2023-02-01 [1] CRAN (R 4.3.0)
#>  digest        0.6.31  2022-12-11 [1] CRAN (R 4.3.0)
#>  evaluate      0.20    2023-01-17 [1] CRAN (R 4.3.0)
#>  fastmap       1.1.1   2023-02-24 [1] CRAN (R 4.3.0)
#>  fs            1.6.1   2023-02-06 [1] CRAN (R 4.3.0)
#>  glue          1.6.2   2022-02-24 [1] CRAN (R 4.3.0)
#>  htmltools     0.5.5   2023-03-23 [1] CRAN (R 4.3.0)
#>  knitr         1.42    2023-01-25 [1] CRAN (R 4.3.0)
#>  lifecycle     1.0.3   2022-10-07 [1] CRAN (R 4.3.0)
#>  magrittr      2.0.3   2022-03-30 [1] CRAN (R 4.3.0)
#>  purrr         1.0.1   2023-01-10 [1] CRAN (R 4.3.0)
#>  R.cache       0.16.0  2022-07-21 [1] CRAN (R 4.3.0)
#>  R.methodsS3   1.8.2   2022-06-13 [1] CRAN (R 4.3.0)
#>  R.oo          1.25.0  2022-06-12 [1] CRAN (R 4.3.0)
#>  R.utils       2.12.2  2022-11-11 [1] CRAN (R 4.3.0)
#>  Rcpp          1.0.10  2023-01-22 [1] CRAN (R 4.3.0)
#>  reprex        2.0.2   2022-08-17 [1] CRAN (R 4.3.0)
#>  rlang         1.1.1   2023-04-28 [1] CRAN (R 4.3.0)
#>  rmarkdown     2.21    2023-03-26 [1] CRAN (R 4.3.0)
#>  rstudioapi    0.14    2022-08-22 [1] CRAN (R 4.3.0)
#>  sessioninfo   1.2.2   2021-12-06 [1] CRAN (R 4.3.0)
#>  styler        1.9.1   2023-03-04 [1] CRAN (R 4.3.0)
#>  terra       * 1.7-37  2023-06-18 [1] CRAN (R 4.3.0)
#>  vctrs         0.6.2   2023-04-19 [1] CRAN (R 4.3.0)
#>  withr         2.5.0   2022-03-03 [1] CRAN (R 4.3.0)
#>  xfun          0.39    2023-04-20 [1] CRAN (R 4.3.0)
#>  yaml          2.3.7   2023-01-23 [1] CRAN (R 4.3.0)
#> 
#>  [1] /home/mikemahoney218/R/x86_64-pc-linux-gnu-library/4.3
#>  [2] /usr/local/lib/R/site-library
#>  [3] /usr/lib/R/site-library
#>  [4] /usr/lib/R/library
#> 
#> ──────────────────────────────────────────────────────────────────────────────

[rhijmans]

I agree and thank you for the helpful repex. It seems to work better now:

library(terra)
test <- rast(ncols = 1000, nrows = 1000, xmin=0)
values(test) <- rnorm(ncell(test))
names(test) <- "name_from_raster"

dummy_model <- list()

terra::predict(test, dummy_model, 
   fun = \(object, newdata) data.frame(x = newdata[[1]] * 0.5)) |> names()
#[1] "x"
 
terra::predict(test, dummy_model, index=1,
   fun = \(object, newdata) data.frame(x = newdata[[1]] * 0.5)) |> names()
#[1] "x"
 
terra::predict(test, dummy_model, index = 1:2, 
   fun = \(object, newdata) data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2)) |> names()
#[1] "x" "y"
 
terra::predict(c(test, setNames(test, "another_name")), dummy_model, index=1:2,
   fun = \(object, newdata) data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2)) |> names()
#[1] "x" "y"
   
terra::predict(c(test, setNames(test, "another_name")), dummy_model, index=c("x", "y"),
   fun = \(object, newdata) data.frame(x = newdata[[1]] * 0.5, y = newdata[[1]] * 2)) |> names()
#[1] "x" "y"

[mikemahoney218]

Fantastic, thank you!