Add zero for classes that that are present in landscape but not sampling plot

[mhesselbarth]

Currently, the sample_lsm() function only returns rows for classes that are present in the sample plot. So if a class is present in the landscape, but not in a specific sample plot, simply no value is returned for this class. Maybe it makes sense to add an argument that automatically adds a 0 for these classes. On example where this makes sense would be the proportion of landcover.

[Nowosad]

@mhesselbarth what do you propose to do for sample plots with NAs (partialy or completely covered by NA)?

[mhesselbarth]

Good question, probably need to think a bit more about this. Maybe if only NA is present, return NA as well. And if some cells are NA, that shouldn't change anything to how metrics are calculated anyways.

[mhesselbarth]

Please have a look at cbfde3f on the branch sample_lsm_update.

sample_lsm() now has an argument all_classes = TRUE that allows returning class level metrics for all classes in the landscape for each sample plot (by adding NA as value if needed).

In the following example, class 1 is not present in both sample plots. So for both class-level metrics an NA row is added. I also added a landscape-level metric to show that different levels can still be combined.

library(landscapemetrics)

sample_points <- matrix(c(25, 15, 5, 25), ncol = 2, byrow = TRUE)

result_sample <- sample_lsm(landscape, y = sample_points,
                            size = 5, shape = "circle",
                            what = c("lsm_c_ca", "lsm_c_pland", "lsm_l_ta"),
                            all_classes = TRUE)
#> Warning: Please use 'check_landscape()' to ensure the input data is valid.

result_sample
#> # A tibble: 14 x 8
#>    layer level     class    id metric   value plot_id percentage_inside
#>    <int> <chr>     <int> <int> <chr>    <dbl>   <int>             <dbl>
#>  1     1 class         1    NA ca     NA            1              102.
#>  2     1 class         2    NA ca      0.0022       1              102.
#>  3     1 class         3    NA ca      0.0058       1              102.
#>  4     1 class         1    NA pland  NA            1              102.
#>  5     1 class         2    NA pland  27.5          1              102.
#>  6     1 class         3    NA pland  72.5          1              102.
#>  7     1 landscape    NA    NA ta      0.008        1              102.
#>  8     1 class         1    NA ca     NA            2              102.
#>  9     1 class         2    NA ca      0.0033       2              102.
#> 10     1 class         3    NA ca      0.0047       2              102.
#> 11     1 class         1    NA pland  NA            2              102.
#> 12     1 class         2    NA pland  41.2          2              102.
#> 13     1 class         3    NA pland  58.8          2              102.
#> 14     1 landscape    NA    NA ta      0.008        2              102.

^{Created on 2020-05-13 by the reprex package (v0.3.0)}

[Nowosad]

Looks good!