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#### 7.1.6 `1d`, `2d`, ...: Isotropic Cartesian Matching

    matcher=1d values*='<x>'
               params='<error>'
               tuning='<bin-factor>'

> `values*`:
>   - `x`: Cartesian co-ordinate #1
> `params`:
>   - `error`: Maximum Cartesian separation for match
> `tuning`:
>   - `bin-factor`: Scaling factor to adjust bin size; larger values mean larger bins

    matcher=2d values*='<x> <y>'
               params='<error>'
               tuning='<bin-factor>'

> `values*`:
>   - `x`: Cartesian co-ordinate #1
>   - `y`: Cartesian co-ordinate #2
> `params`:
>   - `error`: Maximum Cartesian separation for match
> `tuning`:
>   - `bin-factor`: Scaling factor to adjust bin size; larger values mean larger bins

The `1d` matcher compares positions in 1-dimensional Cartesian space. Rows are considered to match if their `x` column values differ by no more than `error`.

The `2d` matcher compares postions in 2-dimensional Cartesian space. Rows are considered to match if the difference in their (`x`,`y`) positions reckoned using Pythagoras is less than `error`.

Matching in any number of Cartesian dimensions can be done by extending this syntax in the obvious way.

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Next: 2d_anisotropic, ...: Anisotropic Cartesian Matching
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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk