R: Examples for 'stars::st_as

### ** Examples

tif = system.file("tif/L7_ETMs.tif", package = "stars")
x = read_stars(tif)
x = x[,1:100,1:100,6] # subset of a band with lower values in it
x[[1]][x[[1]] < 30] = NA # set lower values to NA
x[[1]] = x[[1]] < 100 # make the rest binary
x

stars object with 3 dimensions and 1 attribute
attribute(s):
 L7_ETMs.tif    
 Mode :logical  
 FALSE:525      
 TRUE :7665     
 NA's :1810     
dimension(s):
     from  to  offset delta                     refsys point x/y
x       1 100  288776  28.5 SIRGAS 2000 / UTM zone 25S FALSE [x]
y       1 100 9120761 -28.5 SIRGAS 2000 / UTM zone 25S FALSE [y]
band    6   6      NA    NA                         NA    NA

(p = st_as_sf(x)) # removes NA areas

Simple feature collection with 8190 features and 1 field
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 288776.3 ymin: 9117911 xmax: 291626.3 ymax: 9120761
Projected CRS: SIRGAS 2000 / UTM zone 25S
First 10 features:
     V1                       geometry
1  TRUE POLYGON ((288776.3 9120761,...
2  TRUE POLYGON ((288804.8 9120761,...
3  TRUE POLYGON ((288833.3 9120761,...
4  TRUE POLYGON ((288861.8 9120761,...
5  TRUE POLYGON ((288890.3 9120761,...
6  TRUE POLYGON ((288918.8 9120761,...
7  TRUE POLYGON ((288947.3 9120761,...
8  TRUE POLYGON ((288975.8 9120761,...
9  TRUE POLYGON ((289004.3 9120761,...
10 TRUE POLYGON ((289032.8 9120761,...

(p = st_as_sf(x[,,,1], merge = TRUE)) # glues polygons together

Simple feature collection with 155 features and 1 field
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 288776.3 ymin: 9117911 xmax: 291626.3 ymax: 9120761
Projected CRS: SIRGAS 2000 / UTM zone 25S
First 10 features:
   L7_ETMs.tif                       geometry
1            0 POLYGON ((289517.3 9120761,...
2            0 POLYGON ((290144.3 9120761,...
3            0 POLYGON ((290315.3 9120761,...
4            0 POLYGON ((291113.3 9120761,...
5            0 POLYGON ((291341.3 9120761,...
6            1 POLYGON ((291455.3 9120761,...
7            1 POLYGON ((291569.3 9120761,...
8            0 POLYGON ((290372.3 9120732,...
9            1 POLYGON ((290628.8 9120732,...
10           1 POLYGON ((290771.3 9120732,...

all(st_is_valid(p)) # not all valid, see details

[1] TRUE

plot(p, axes = TRUE)

(p = st_as_sf(x, na.rm = FALSE, merge = TRUE)) # includes polygons with NA values

Simple feature collection with 380 features and 1 field
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 288776.3 ymin: 9117911 xmax: 291626.3 ymax: 9120761
Projected CRS: SIRGAS 2000 / UTM zone 25S
First 10 features:
   L7_ETMs.tif                       geometry
1            0 POLYGON ((289517.3 9120761,...
2            0 POLYGON ((290144.3 9120761,...
3            0 POLYGON ((290315.3 9120761,...
4            0 POLYGON ((291113.3 9120761,...
5            0 POLYGON ((291341.3 9120761,...
6            1 POLYGON ((291455.3 9120761,...
7            1 POLYGON ((291569.3 9120761,...
8           NA POLYGON ((289745.3 9120732,...
9           NA POLYGON ((289830.8 9120732,...
10           0 POLYGON ((290372.3 9120732,...

plot(p, axes = TRUE)

Examples for 'stars::st_as_sf'

Convert stars object into an sf object