shapewrite - Write geographic data structure to shapefile

Syntax

shapewrite(S, filename) shapewrite(S, filename, 'DbfSpec', dbfspec)

Description

shapewrite(S, filename) writes a geographic data structure to disk in shapefile format. shapewrite creates three output files: [basename '.shp'], [basename '.shx'], and [basename '.dbf'], where basename is filename without its extension. If a given attribute is integer-valued for all features, then it is written to the [basename '.dbf'] file as an integer. If an attribute is non-integer-valued for any feature, then it is written as a fixed point decimal value with six digits to the right of the decimal place.

shapewrite(S, filename, 'DbfSpec', dbfspec) writes a shapefile in which the content and layout of the DBF file is controlled by a DBF specification, indicated here by the parameter value dbfspec.

Tips

The xBASE (.dbf) file specifications require that geostruct and mapstruct attribute names are truncated to 11 characters when copied as DBF field names. Consider shortening long field names before calling shapewrite. By doing this, you make field names in the DBF file more readable and avoid introducing duplicate names as a result of truncation.
Remember to set your character encoding scheme to match that of the geographic data structure you are exporting. For instance, if you are exporting a map that displays Japanese text, configure your machine to support Shift-JIS character encoding.

Input Arguments

S

A valid mapstruct or geostruct with specific restrictions on its attribute fields:

Each attribute field value must be either a real, finite, scalar double or a character string.
The type of a given attribute must be consistent across all features.

filename

A character string specifying the output file name and location. If an extension is included, it must be '.shp' or '.SHP'.

'DbfSpec', dbfspec

A scalar MATLAB structure containing one field for each feature attribute to be included in the output shapefile. To include an attribute in the output, provide a field in dbfspec with a name identical to the attribute name as given in S. Assign to that field a scalar structure with the following four fields:

FieldName — The field name to be used in the file
FieldType — The field type to be used in the file ('N' or 'C')
FieldLength — The field length in the file, in bytes
FieldDecimalCount — For numeric fields, the number of digits to the right of the decimal place

Call makedbfspec to construct a DBF spec. Modify the output to remove attributes or change the FieldName, FieldLength, or FieldDecimalCount for one or more attributes.

Examples

Derive a shapefile from concord_roads.shp in which roads of CLASS 5 and greater are omitted. Note the use of the 'Selector' option in shaperead, together with an anonymous function, to read only the main roads from the original shapefile.

shapeinfo('concord_roads')  % 609 features

ans = 
       Filename: [3x67 char]
      ShapeType: 'PolyLine'
    BoundingBox: [2x2 double]
    NumFeatures: 609
     Attributes: [5x1 struct]

S = shaperead('concord_roads', 'Selector', ...
    {@(roadclass) roadclass < 4, 'CLASS'});
shapewrite(S, 'main_concord_roads.shp')
shapeinfo('main_concord_roads')  % 107 features

ans = 
       Filename: [3x24 char]
      ShapeType: 'PolyLine'
    BoundingBox: [2x2 double]
    NumFeatures: 107
     Attributes: [5x1 struct]