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## Manuals

### maplink

#### Description

draw a map with links between locations, indicating the similarity of those locations

the result is an Encapsulated PostScript image

#### Synopsis

maplink [-c float] [-C float] [-D] [-G] [-e] [-g] [-o filename] [-r] configfile differencefile

#### Options

-c
  first contrast parameter, default 1.0
  useful values usually between 0.5 and 5, must be positive
-C
  second contrast parameter, default 0.0
  useful values usually between -0.5 and 0.5, must be less than 1
-D
  maximum difference (fraction, default: 0.9)
-G
  maximum geographic distance (fraction, default: 0.3)
-e
  equal scaling of positive and negative values
-g
  use greyscale
-o filename
  output file
-r
  reverse values

#### Purpose

This program draws lines between locations with a colour showing the similarity between the location. Darker lines mean higher similarity. The input file is a difference matrix file. Missing values (NA) in the input are allowed.

This is the only program tat accepts negative input values. When there are negative values, the lines get a diverging colours. Blue for negative, white for values near zero, and red for positive values.

#### Contrast

See the manual of mapdiff for a description.

#### Limiting the number of lines

By default, only part of the links between locations is drawn. There are two ways in which the number of links is reduced.

First, links between locations that are too far apart geographically are omitted. This limit is controlled by the option `-G`. This option takes a value between 0 and 1. Set this value to 0.3, and only those lines are drawn that are no longer than 0.3 times the length of the longest line. Set this value to 1 if you want all lines.

Second, links that are too light are omitted. This limit is controlled by the option `-D`. This option takes a value between 0 and 1. Set this value to 0.9, and only lines with a darkness of 0.9 or less are drawn. A darkness of 0 is the darkest, a darkness of 1 is white (invisible). Set this value to 1 if you want all lines.