blvim (version 0.1.1)

fortify.sim: Turn a spatial interaction model into a data frame

Description

This function extracts from a spatial interaction model different types of data frame that can be used to produce graphical representations. autoplot.sim() leverages this function to produce its graphical representations.

Usage

# S3 method for sim
fortify(
  model,
  data,
  flows = c("full", "destination", "attractiveness"),
  with_names = FALSE,
  with_positions = FALSE,
  cut_off = 100 * .Machine$double.eps^0.5,
  ...
)

Value

a data frame, see details

Arguments

model

a spatial interaction model object

data

not used

flows

"full" (default), "destination" or "attractiveness", see details.

with_names

specifies whether the extracted data frame includes location names (FALSE by default)

with_positions

specifies whether the extracted data frame is based on location positions (FALSE by default)

cut_off

cut off limit for inclusion of a flow row in the final data frame.

...

additional parameters, not used currently

Details

The data frame produced by the method depends on the values of flows and with_positions. The general principal is to have one row per flow, either a single flow from an origin location to a destination location, or an aggregated flow to a destination location. Flows are stored in one column of the data frame, while the other columns are used to identify origin and destination.

If with_position is FALSE (default value), data frames are simple. Depending on flows, the function extracts different data frames:

• "full": this is the default case for which the full flow matrix is extracted. The data frame has three variables:

  • origin: identifies the origin location by its index from 1 to the number of origin locations

  • destination: identifies the destination location by its index from 1 to the number of destination locations

  • flow: the flow between the corresponding location It is recommend to use flows_df() for more control over the extraction outside of simple graphical representations.

• "destination": the data frame has only two or three columns:

  • destination: identifies the destination location by its index from 1 to the number of destination locations

  • flow: the incoming flows (see destination_flow())

  • name: the name of the destination location if with_names is TRUE

• "attractiveness": the data frame has also two ot three columns, destination and name as in the previous case and attractiveness which contains the attractivenesses of the destinations (see attractiveness()).

When the with_positions parameter is TRUE, the location positions (location_positions()) are used to produce more "geographically informed" extractions. Notice that if no positions are known for the locations, the use of with_positions = TRUE is an error. Depending on flows we have the following representations:

• "full": this is the default case for which the full flow matrix is extracted. Positions for both origin and destination locations are needed. The data frame contains five columns:

  • the first two columns are used for the coordinates of the origin locations (see below for the names of the columns)

  • xend and yend are used for the coordinates of the destination locations

  • flow is used for the flows

• "destination" and "attractiveness" produce both a data frame with three or four columns. As when with_positions is FALSE, one column is dedicated either to the incoming flows (destination_flow()) for flows="destination" (the name of the column is destination) or to the attractivenesses (attractiveness()), in which case its name is attractiveness. The other two columns are used for the positions of the destination locations. Their names are the names of the columns of the positions (colnames(destination_location(object))) or "x" and "y", when such names are not specified. If with_names is TRUE, a name column is included and contains the names of the destination locations.

In the position based data frames, rows are excluded from the returned data frames when the flow they represent are small, i.e. when they are smaller than the cut_off value.

See Also

autoplot.sim(), flows_df()

Examples

positions <- matrix(rnorm(10 * 2), ncol = 2)
colnames(positions) <- c("X", "Y")
distances <- as.matrix(dist(positions))
production <- rep(1, 10)
attractiveness <- c(2, rep(1, 9))
flows <- blvim(distances, production, 1.5, 4, attractiveness,
  origin_data =
    list(names = LETTERS[1:10], positions = positions),
  destination_data =
    list(names = LETTERS[1:10], positions = positions)
)
ggplot2::fortify(flows)
ggplot2::fortify(flows, flows = "destination")
ggplot2::fortify(flows, flows = "attractiveness")
## positions
ggplot2::fortify(flows, flows = "attractiveness", with_positions = TRUE)
## names and positions
ggplot2::fortify(flows,
  flows = "destination", with_positions = TRUE,
  with_names = TRUE
)
ggplot2::fortify(flows, with_positions = TRUE, cut_off = 0.1)