Wichtig
Übersetzen ist eine Gemeinschaftsleistung Sie können mitmachen. Diese Seite ist aktuell zu 62.12% übersetzt.
32.4. Anhang D: QGIS R Skriptsyntax
Contributed by Matteo Ghetta - funded by Scuola Superiore Sant’Anna
Writing R scripts in Processing is a bit tricky because of the special syntax.
A Processing R script starts with defining its Inputs and
Outputs, each preceded with double hash characters (##
).
Before the inputs, the group to place the algoritm in can be specified. If the group already exists, the algorithm will be added to it, if not, the group will be created. In the example below, the name of the group is My group:
##My Group=group
32.4.1. Eingaben
All input data and parameters have to be specified. There are several types of inputs:
vector:
##Layer = vector
vector field:
##F = Field Layer
(where Layer is the name of an input vector layer the field belongs to)raster:
##r = raster
table:
##t = table
number:
##Num = number
string:
##Str = string
boolean:
##Bol = boolean
elements in a dropdown menu. The items must be separated with semicolons
;
:##type=selection point;lines;point+lines
32.4.2. Ausgaben
Genau wie die Eingaben müssen alle Ausgaben am Beginn des Skriptes definiert werden:
vector:
##output= output vector
raster:
##output= output raster
table:
##output= output table
plots:
##output_plots_to_html
(##showplots in earlier versions)To show R output in the Result Viewer, put
>
in front of the command whose output you would like to show.
32.4.3. Syntax Summary for QGIS R scripts
A number of input and output parameter types are offered.
32.4.3.1. Input parameter types
Parameter |
Syntax Beispiel |
Rückgabeobjekte |
---|---|---|
vector |
Layer = vector |
sf object (or SpatialDataFrame object, if ##load_vector_using_rgdal is specified) |
vector point |
Layer = vector point |
sf object (or SpatialDataFrame object, if ##load_vector_using_rgdal is specified) |
vector line |
Layer = vector line |
sf object (or SpatialDataFrame object, if ##load_vector_using_rgdal is specified) |
vector polygon |
Layer = vector polygon |
sf object (or SpatialPolygonsDataFrame object, if ##load_vector_using_rgdal is used) |
multiple vector |
Layer = multiple vector |
sf object (or SpatialDataFrame objects if ##load_vector_using_rgdal is specified) |
table |
Layer = table |
Datenrahmenumwandlung von csv, voreingestelltes Objekt der |
field |
Field = Field Layer |
Name des ausgewählten Feldes, z.B. |
raster |
Layer = raster |
RasterBrick Objekt, voreingestelltes Objekt des |
multiple raster |
Layer = multiple raster |
RasterBrick Objekt, voreingestelltes Objekt des |
number |
N = number |
gewählte Ganzzahl oder Fließkommazahl |
string |
S = string |
in der Box eingefügte Zeichenkette |
longstring |
LS = longstring |
in der Box eingefügte Zeichenkette, kann länger als eine normale Zeichenkette sein |
selection |
S = selection first;second;third |
Zeichenkette des im dropdown-Menü gewählten Objektes |
crs |
C = crs |
Zeichenkette des sich ergebenen KBS im Format: |
extent |
E = extent |
Ausdehnungsobjekt des |
point |
P = point |
beim Klicken auf die Karte erhält man die Koordinaten des Punktes |
file |
F = file |
Pfad der gewählten Datei, z.B. „/home/matteo/file.txt“ |
folder |
F = folder |
Pfad des gewählten Ordners, z.B „/home/matteo/Downloads“ |
A parameter can be OPTIONAL, meaning that it can be ignored.
In order to set an input as optional, you add the string optional
before the input, e.g:
##Layer = vector
##Field1 = Field Layer
##Field2 = optional Field Layer
32.4.3.2. Output parameter types
Parameter |
Syntax Beispiel |
---|---|
vector |
Output = output vector |
raster |
Output = output raster |
table |
Output = output table |
file |
Output = output file |
Bemerkung
You can save plots as png
from the Processing Result Viewer, or you can choose to
save the plot directly from the algorithm interface.
32.4.3.3. Skript Hauptteil
The script body follows R syntax and the Log panel can help you if there is something wrong with your script.
Remember that you have to load all additional libraries in the script:
library(sp)
32.4.4. Beispiele
32.4.4.1. Beispiel mit Vektorausgabe
Sehen wir uns einen Algorithmus aus der Onlinesammlung an, der zufällige Punkte innerhalb der Ausdehnung eines Eingabelayers erstellt:
##Point pattern analysis=group
##Layer=vector polygon
##Size=number 10
##Output=output vector
library(sp)
spatpoly = as(Layer, "Spatial")
pts=spsample(spatpoly,Size,type="random")
spdf=SpatialPointsDataFrame(pts, as.data.frame(pts))
Output=st_as_sf(spdf)
Explanation (per line in the script):
Point pattern analysis
ist die Gruppe des AlgorithmusLayer
ist der EingabevektorlayerSize
is a numerical parameter with a default value of 10Output
ist der Vektorlayer der vom Algorithmus erstellt wirdlibrary(sp)
loads the sp libraryspatpoly = as(Layer, "Spatial")
translate to an sp objectCall the
spsample
function of thesp
library and run it using the input defined above (Layer
andSize
)Create a SpatialPointsDataFrame object using the
SpatialPointsDataFrame
functionCreate the output vector layer using the
st_as_sf
function
That’s it! Just run the algorithm with a vector layer you have in the QGIS Legend, choose the number of random point. The resulting layer will be added to your map.
32.4.4.2. Beispiel mit Rasterausgabe
The following script will perform basic ordinary kriging to
create a raster map of interpolated values from a specified field
of the input point vector layer by using the autoKrige
function of the automap
R package.
It will first calculate the kriging model and then create a
raster.
The raster is created with the raster
function of the raster R
package:
##Basic statistics=group
##Layer=vector point
##Field=Field Layer
##Output=output raster
##load_vector_using_rgdal
require("automap")
require("sp")
require("raster")
table=as.data.frame(Layer)
coordinates(table)= ~coords.x1+coords.x2
c = Layer[[Field]]
kriging_result = autoKrige(c~1, table)
prediction = raster(kriging_result$krige_output)
Output<-prediction
By using ##load_vector_using_rgdal
, the input vector layer
will be made available as a SpatialDataFrame
objects,
so we avoid having to translate it from an sf
object.
32.4.4.3. Beispiel mit Tabellenausgabe
Lassen Sie uns den Algorithmus Summary Statistics
bearbeiten, so dass als Ausgabe eine Tabelle (csv) erzeugt wird.
Der Hauptteil des Skriptes sieht wie folgt aus:
##Basic statistics=group
##Layer=vector
##Field=Field Layer
##Stat=Output table
Summary_statistics<-data.frame(rbind(
sum(Layer[[Field]]),
length(Layer[[Field]]),
length(unique(Layer[[Field]])),
min(Layer[[Field]]),
max(Layer[[Field]]),
max(Layer[[Field]])-min(Layer[[Field]]),
mean(Layer[[Field]]),
median(Layer[[Field]]),
sd(Layer[[Field]])),
row.names=c("Sum:","Count:","Unique values:","Minimum value:","Maximum value:","Range:","Mean value:","Median value:","Standard deviation:"))
colnames(Summary_statistics)<-c(Field)
Stat<-Summary_statistics
Die dritte Zeile gibt als Eingabe Vector Field vor. In der vierten Zeile wird die Ausgabe des Algorithmus als Tabelle festgelegt.
In der letzten Zeile wird das im Skript erstellte Objekt Stat
in eine csv
Tabelle umgewandelt.
32.4.4.4. Beispiel mit Konsolenausgabe
We can use the previous example and instead of creating a table, print the result in the Result Viewer:
##Basic statistics=group
##Layer=vector
##Field=Field Layer
Summary_statistics<-data.frame(rbind(
sum(Layer[[Field]]),
length(Layer[[Field]]),
length(unique(Layer[[Field]])),
min(Layer[[Field]]),
max(Layer[[Field]]),
max(Layer[[Field]])-min(Layer[[Field]]),
mean(Layer[[Field]]),
median(Layer[[Field]]),
sd(Layer[[Field]])),row.names=c("Sum:","Count:","Unique values:","Minimum value:","Maximum value:","Range:","Mean value:","Median value:","Standard deviation:"))
colnames(Summary_statistics)<-c(Field)
>Summary_statistics
The script is exactly the same as the one above except for two edits:
no output specified (the fourth line has been removed)
the last line begins with
>
, telling Processing to make the object available through the result viewer
32.4.4.5. Beispiel mit Plot
To create plots, you have to use the ##output_plots_to_html
parameter as in the following script:
##Basic statistics=group
##Layer=vector
##Field=Field Layer
##output_plots_to_html
####output_plots_to_html
qqnorm(Layer[[Field]])
qqline(Layer[[Field]])
The script uses a field (Field
) of a vector layer (Layer
) as
input, and creates a QQ Plot (to test the normality of the
distribution).
The plot is automatically added to the Processing Result Viewer.