17.31. Use R scripts in Processing¶

17.31.2.1. Script parameters¶

Open the editor and start writing at the beginning of it.

You must specify some parameters before the script body:

1. the name of the group in which you want to put your script:

   ##plots=group
   

   so you will find your script in the plots group in the Processing toolbox.

2. you have to tell Processing that you want to display a plot (just in this example):

   ##showplots
   

   this way in the Result Viewer of Processing you’ll see the plot.

3. You need also to tell Processing with which kind of data you are working with. In this example we want to create a plot from a field of a vector layer:

   ##Layer=vector
   

   Processing knows now that the input is a vector. The name Layer is not important, what matters is the vector parameter.

4. Finally, you have to specify the input field of the vector layer you want to plot:

   ##X=Field Layer
   

   So Processing knows that you have called X the Field Layer.

17.31.2.2. Script body¶

Now that you have set up the heading of the script you can add the function:

boxplot(Layer[[X]])

Notice that boxplot is the name of the R function itself that calls Layer as dataset and X as the field of the dataset.

The final script looks like this:

##Vector processing=group
##showplots
##Layer=vector
##X=Field Layer
boxplot(Layer[[X]])

Save the script in the default path suggested by Processing. The name you choose will be the same as the name of the script you’ll find in the Processing toolbox.

Now just run it using the button on the top of the editor window:

Otherwise, once the editor window has been closed, use the text box of Processing to find your script:

You are now able to fill the parameters required in the Processing algorithm window:

• as Layer choose the sample points one
• fill the X field with the value parameter

Click on Run.

The Result window should be automatically opened, if not, just click on Processing ‣ Result Viewer....

This is the final result you’ll see:

17.31.3.1. Script parameters¶

As before we have to set some parameters before the script body:

1. specify the name of the group in which you want to put your script, for example Point pattern analysis:

   ##Point pattern analysis=group
   

2. set the layer that will contain the random points:

   ##Layer=vector
   

3. set the number of points that are going to be created:

   ##Size=number 10
   

   Nota

   10 is going to be the default value. You can change this number or you can leave the parameter without a default number

4. specify that the output is a vector layer:

   ##Output= output vector
   

17.31.3.2. Script body¶

Now you can add the body of the function:

1. run the spsample function:

   pts=spsample(Layer,Size,type="random")
   

   this way the function takes the extent of the Layer, the number of points is taken from the Size parameter and the point generation is random

2. Write the line that contains the parameters of the output:

   Output=SpatialPointsDataFrame(pts, as.data.frame(pts))

The final script should look like:

Save it and run it, clicking on the running button.

In the new window type in the right parameters:

and click on run.

Resulting points will be displayed in the map canvas