Installation

# install.packages("devtools")devtools::install_github("hypertidy/area")

Straightforward tools

library(area)polygon_area(cbind(c(0,1,1,0,0),                 c(0,0,1,1,0)))#> [1] 1triangle_area(cbind(c(0,1,1,1,0,0),                c(0,0,1,1,1,0)))#> [1] 0.5 0.5

index<-4423## explain lateridx<- c(tas$S[1],tas$S[1:index,2],1)plot(tas$P[idx, ],type="l",asp=1)

polygon_area(tas$P[idx, ])/1e6#> [1] 61672.74sf::st_area(sf::st_polygon(list(tas$P[idx, ])))/1e6#> [1] 61672.74

library(dplyr)library(area)calc_area<-function(df) {area<-df %>% mutate(row= row_number()) %>%   group_by(multipolygon_id,polygon_id,linestring_id) %>%    arrange(row) %>%   summarize(area= polygon_area(cbind(x,y))) %>%   ungroup()#%>%area %>%  mutate(area=area,hole= c(-1,1)[(pmax(c(1, diff(multipolygon_id)), c(1, diff(polygon_id)))==1)+1])}xsf<-silicate::inlandwatersdf<-sfheaders::sf_to_df(xsf)(mmarea<- calc_area(df))#> `summarise()` has grouped output by 'multipolygon_id', 'polygon_id'. You can#> override using the `.groups` argument.#> # A tibble: 189 × 5#>    multipolygon_id polygon_id linestring_id          area  hole#>              <dbl>      <dbl>         <dbl>         <dbl> <dbl>#>  1               1          1             1   2203380098.     1#>  2               2          1             1    103039733.     1#>  3               3          1             1 750145539384.     1#>  4               3          1             2    100909770.    -1#>  5               3          1             3   2203380098.    -1#>  6               3          1             4     45585186.    -1#>  7               3          1             5     89780792.    -1#>  8               3          1             6    110755146.    -1#>  9               3          1             7     59287239.    -1#> 10               3          1             8     66189369.    -1#> # ℹ 179 more rowssum(mmarea$area*mmarea$hole)#> [1] 1.923706e+12sum(sf::st_area(xsf))#> old-style crs object detected; please recreate object with a recent sf::st_crs()#> old-style crs object detected; please recreate object with a recent sf::st_crs()#> old-style crs object detected; please recreate object with a recent sf::st_crs()#> 1.923706e+12 [m^2]

Straightforward?

(a<- triangle_area(mm_tri$P[t(mm_tri$T), ]))#>  [1] 0.03000 0.06900 0.03000 0.02000 0.05000 0.10000 0.05500 0.03000 0.03000#> [10] 0.03000 0.03000 0.14550 0.05145 0.04500 0.11250 0.06250 0.06800sum(a)#> [1] 0.95895## that is the area of the silicate::minimal_mesh (but the hole is included)

library(silicate)#>#> Attaching package: 'silicate'#> The following objects are masked _by_ '.GlobalEnv':#>#>     inlandwaters, minimal_mesh#> The following object is masked from 'package:stats':#>#>     filtertas_tri<-RTriangle::triangulate(tas)trxy<-tas_tri$P[t(tas_tri$T), ]dim(trxy)#> [1] 18291     2rbenchmark::benchmark(R= {a<- tri_area(trxy)},cpp= {b<- triangle_area(trxy)})#>   test replications elapsed relative user.self sys.self user.child sys.child#> 2  cpp          100   0.047    1.000     0.035    0.012          0         0#> 1    R          100   0.215    4.574     0.202    0.012          0         0sum(abs(a-b))#> [1] 0.0004653583mean(c(sum(a), sum(b)))#> [1] 61672735794

Code of Conduct