A species dataframe with x (long), y (lat) and optional other variables.
colspxy
The range of columns for x (long) and y (lat) in dfsp.
colspkept
The columns of dfsp that should be kept in the final dataframe (default: xy).
dfvar
A dataframe object with x, y and environmental variables.
colvarxy
The range of columns for x and y in dfvar.
colvar
The range of enviromental variable columns in dfvar (default: all except xy).
resolution
The distance between x,y of species and environmental datafreme beyond which values shouldn't be added.
Details
The xy (lat/long) coordinates of the species occurrences are compared to those of the environment dataframe and the value of the closest pixel is added to the species dataframe. When the closest environment pixel is more distant than the given resolution, NA is added instead of the value. This function is similar to sample() in ArcGIS.
Value
A Dataframe with the same rows as dfsp, with environmental values from dfvar in column.