Dear community
This example code works
library(raster)
library(sp)
library(rgdal)
library(ggplot2)
# Create some sample raster data
raster_file <- raster(ncol=36, nrow=18)
raster_file[] <- 1:ncell(raster_file)
plot(raster_file)
#Create some sample polygons
cds1 <- rbind(c(-180,-20), c(-160,5), c(-60, 0), c(-160,-60), c(-180,-20))
cds2 <- rbind(c(80,0), c(100,60), c(120,0), c(120,-55), c(80,0))
shape_file <- SpatialPolygons(list(Polygons(list(Polygon(cds1)), 1),
Polygons(list(Polygon(cds2)), 2)))
plot(shape_file)
# Extract raster values within the shapefile
extracted_values <- extract(raster_file, shape_file)
# Assuming the shapefile has multiple polygons and you want to create a
boxplot for each
data_list <- lapply(1:length(extracted_values), function(i) {
data.frame(value = extracted_values[[i]], polygon = i)
})
data <- do.call(rbind, data_list)
# Create the boxplot
bp<-ggplot(data, aes(x = factor(polygon), y = value)) +
geom_boxplot() +
labs(x = "Polygon", y = "Raster Values") +
theme_minimal()
bp
For my own dataset I encountered problems in reading in the polygons.
The error message comes in the boxplot function
Here may shape file
> # load shape file including all layers and print layers
> shape_file<-shapefile("C:/Users/.....BiogeoRegion.shp")
Warning message:
[vect] Z coordinates ignored
> names(shape_file)
[1] "RegionNumm" "RegionName" "Unterregio" "Unterreg_1" "ObjNummer"
"Version" "Shape_Leng" "Shape_Area" "DERegionNa" "FRRegionNa"
[11] "ITRegionNa" "DEBioBedeu" "FRBioBedeu" "ITBioBedeu"
> str(shape_file)
Formal class 'SpatialPolygonsDataFrame' [package "sp"] with 5 slots
..@ data :'data.frame': 12 obs. of 14 variables:
.. ..$ RegionNumm: int [1:12] 1 2 2 2 2 3 3 4 5 5 ...
.. ..$ RegionName: chr [1:12] "R1" "R2" "R2" "R2" ...
.. ..$ Unterregio: int [1:12] 11 21 22 23 24 31 32 41 51 52 ...
.. ..$ Unterreg_1: chr [1:12] "U11" "U21" "U22" "U23" ...
.. ..$ ObjNummer : chr [1:12] "1" "2" "3" "4" ...
.. ..$ Version : chr [1:12] "2020/05/08" "2020/05/08" "2020/05/08"
"2020/05/08" ...
.. ..$ Shape_Leng: num [1:12] 725117 334364 539746 576810 555541 ...
.. ..$ Shape_Area: num [1:12] 4.17e+09 1.11e+09 1.07e+09 4.64e+09 4.47e+09
...
.. ..$ DERegionNa: chr [1:12] "Jura" "Mittelland" "Mittelland"
"Mittelland" ...
.. ..$ FRRegionNa: chr [1:12] "Jura" "Plateau" "Plateau" "Plateau" ...
.. ..$ ITRegionNa: chr [1:12] "Giura" "Altipiano" "Altipiano" "Altipiano"
...
.. ..$ DEBioBedeu: chr [1:12] "Jura und Randen" "Genferseegebiet"
"Hochrheingebiet" "Westliches Mittelland" ...
.. ..$ FRBioBedeu: chr [1:12] "Jura et Randen" "Bassin lémanique" "Bassin
rhénan" "Plateau occidental" ...
.. ..$ ITBioBedeu: chr [1:12] "Giura e Randen" "Regione del Lemano"
"Regione dellAlto Reno" "Altipiano occidentale" ...
..@ polygons :List of 12
> # select a specific raster file from a list
> raster_file<-allrasters_pres[[1]]
> names(raster_file)
[1] "Andrena.barbilabris_glo_ensemble"
>
> # Extract raster values within the shapefile
> extracted_values <- extract(raster_file, shape_file)
>
>
>
> # Assuming the shapefile has multiple polygons and you want to create a
boxplot for each
> data_list <- lapply(1:length(extracted_values), function(i) {
+ data.frame(value = extracted_values[[i]], polygon = i)
+ })
> data <- do.call(rbind, data_list)
> names(data)
[1] "value" "polygon"
>
> # Create the boxplot
> bp<-ggplot(data, aes(x = factor(polygon), y = value)) +
+ geom_boxplot() +
+ labs(x = "Polygon", y = "Raster Values") +
+ theme_minimal()
> bp
Error in UseMethod("depth") :
no applicable method for 'depth' applied to an object of class "NULL"
In addition: Warning message:
Removed 452451 rows containing non-finite outside the scale range
(`stat_boxplot()`).
>
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