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ACON Home/Topics | Commands

ShapeFile Functions

These ShapeFile functions are based on the ShapeLib library available at shapelib.maptools.org. These bindings presented here are similar to, but not identical to the original C library.

The ShapeFile functions include:

Shp_Dbf_Create, DBF_Create, DBF_Open, DBF_Close, DBF_Read_String_Attribute, DBF_Get_Field_Info, DBF_Get_Field_Count, DBF_Get_Record_Count, DBF_Write_Integer_Attribute, DBF_Write_Double_Attribute, DBF_Write_String_Attribute, DBF_Add_Field, SHP_Create, SHP_Open, SHP_Close, SHP_Create_Object, SHP_Destroy_Object, SHP_Create_Simple_Object, SHP_Write_Object, SHP_Read_Object, and SHP_Get_Info.

SHP_DBF_Create

This command creates a Point Shapefile and matching DBF attribute file.

There are 4 parameters:: ShapefileName - name of the shapefile to create.; lonVector - a vector containing the longitude values.; latVector - a vector containing the latitude values.; attributenameMatrix - a character matrix providing the names of the attributes associated with each data point.

SHP_DBF_Create(shapefilename,lonVector,latVector,attributenameMatrix);


lon = -66.5 -65 -64.;

lat = 44 44.3 46;

catch = 10 20 30.;

species = strfold(";Cod Cod Haddock";);

attributes = strfold(";Catch species";);

// Create a shape file with 3 data points, and 2 attributes per point

SHP_DBF_Create("C:/myShapeFile",lon,lat,attributes);

DBF_Create

This command creates a DBF attribute file (commonly used as the dual to a shapefile).

There is 1 parameter:: dfbfilename - name of the dbf file to create.

DBFHandle = DBF_Create(dbffilename);


dbfhdl = DBF_Create("C:/myDBFfile");

DBF_Open

This command opens an existing DBF attribute file (commonly used as the dual to a shapefile). A handle to the open file is returned.

There are 2 parameter:: dfbfilename - name of the dbf file to open.; accessflag - type of access; "rb" (read-only binary) and "rb+" (read/write binary).

DBFHandle = DBF_Open(dbffilename,accessflag);


dbfhdl = DBF_Open("C:/myDBFfile","rb");

DBF_Close

This command closes a DBF attribute file (commonly used as the dual to a shapefile).

There is 1 parameter:: dfbhandle - The DBF handle of the dbf file to close.

DBF_Close(dbfhandle);


DBF_Close(dbfhdl);

DBF_Read_String_Attribute

This command closes a DBF attribute file (commonly used as the dual to a shapefile).

There are 3 parameters:: dfbhandle - The DBF handle of the dbf file to use.; shapenumber - The record number from which the field is read.; fieldnumber - The field number of the field to read.

textstring = DBF_Read_String_Attribute(dbfhandle,shapenumber,fieldnumber);


a = DBF_Read_String_Attribute(dbfhandle,0,0); // read the 1st field from the 1st row

This command returns information about a field in a DBF attribute file (commonly used as the dual to a shapefile). An enclosed vector is returned containing 3 elements: the name of the field, the width of the field, and the number of decimal places for a non-integer numeric field.

There are 2 parameters:: dfbhandle - The DBF handle of the dbf file to use.; fieldnumber - The field number of the field to read.

enclosedvector = DBF_Get_Field_Info(dbfhandle,fieldnumber);


enclosedvector = DBF_Get_Field_Info(dbfhandle,0); // read the 1st field information

print(enclosedvector[1]);

TEST

print(enclosedvector[2]);

10

print(enclosedvector[3]);

0

DBF_Get_Field_Count

This command returns the number of fields in a DBF attribute file (commonly used as the dual to a shapefile).

There is 1 parameter:: dfbhandle - The DBF handle of the dbf file to use.

nfields = DBF_Get_Field_Count(dbfhandle);


nfields = DBF_Get_Field_Count(dbfhandle); // read the number of fields

DBF_Get_Record_Count

This command returns the number of records in a DBF attribute file (commonly used as the dual to a shapefile).

There is 1 parameter:: dfbhandle - The DBF handle of the dbf file to use.

nrecords = DBF_Get_Record_Count(dbfhandle);


nrecords = DBF_Get_Record_Count(dbfhandle); // read the number of records

DBF_Write_Integer_Attribute

This command writes an integer to a DBF attribute file (commonly used as the dual to a shapefile).

There are 4 parameters:: dfbhandle - The DBF handle of the dbf file to use.; shapenumber - The record number to which the field is written.; fieldnumber - The field number of the field to write.; value - The integer value to write.

result = DBF_Write_Integer_Attribute(dbfhandle,shapenumber,fieldnumber,value);


result = DBF_Write_Integer_Attribute(dbfhandle,0,0,621); // write the value 621 as the 1st attribute in the 1st row

DBF_Write_double_Attribute

This command writes an floating point value (double) to a DBF attribute file (commonly used as the dual to a shapefile).

There are 4 parameters:: dfbhandle - The DBF handle of the dbf file to use.; shapenumber - The record number to which the field is written.; fieldnumber - The field number of the field to write.; value - The value to write.

result = DBF_Write_Double_Attribute(dbfhandle,shapenumber,fieldnumber,value);


result = DBF_Write_Double_Attribute(dbfhandle,0,0,3.1415); // write the value 3.1415 as the 1st attribute in the 1st row

DBF_Write_string_Attribute

This command writes an string value to a DBF attribute file (commonly used as the dual to a shapefile).

There are 4 parameters:: dfbhandle - The DBF handle of the dbf file to use.; shapenumber - The record number to which the field is written.; fieldnumber - The field number of the field to write.; value - The value to write.

result = DBF_Write_String_Attribute(dbfhandle,shapenumber,fieldnumber,value);


result = DBF_Write_String_Attribute(dbfhandle,0,0,"TEST"); // write "TEST" as the 1st attribute in the 1st row

SHP_Create

This command creates a SHP file.

There are 2 parameters:: shpfilename - name of the shp file to create.; shptype - type shp file to create: 1 = point, 3 = arc, 5 = polygon, 8 = multipoint.

SHPHandle = SHP_Create(shpfilename,shptype);


shphdl = SHP_Create("C:/mySHPfile",1);

SHP_Open

This command opens an existing SHP attribute file. A handle to the open file is returned.

There are 2 parameter:: dfbfilename - name of the shp file to open.; accessflag - type of access; "rb" (read-only binary) and "rb+" (read/write binary).

SHPHandle = SHP_Open(shpfilename,accessflag);


shphdl = SHP_Open("C:/mySHPfile","rb");

SHP_Close

This command closes a SHP attribute file.

There is 1 parameter:: shphandle - The SHP handle of the shp file to close.

SHP_Close(shpfilhandle);


SHP_Close(shphdl);

SHP_Create_Object

This command creates a shape object in memory that can be written to a shape file. A handle to the object is returned.

There are 7 to 9 parameters:: shapetype - type of shape to create: 1 = point, 3 = arc, 5 = polygon, 8 = multipoint.; shapeid - integer id of shape to create.; nparts - number of parts in the shape.; partstart - integer value giving the part start index.; parttype - integer part type of the part being created.; x vector - vector of x coordinates.; y vector - vector of y coordinates.; z vector - optional vector of z coordinates.; m vector - optional vector of measure values.

shpObject = SHP_Create_Object(type,shapeID,nparts,partstart,parttype,x vector,y vector[,z vector[,m vector]]);

myShpObject = SHP_Create_Object(1,1,0,$null,$null,-66 -67 -65.5,43 44 45.6,1 2 3.);

SHP_Destroy_Object

This command removes a shape object from memory.

There is 1 parameter:: shapeobject - The handle of the shape object to remove.

SHP_Destroy_Object(shapeobject);


SHP_Destroy_Object(shapeobject);

SHP_Create_Simple_Object

This command creates a shape object in memory that can be written to a shape file. A handle to the object is returned.

There are 3 or 4 parameters:: shapetype - type of shape to create: 1 = point, 3 = arc, 5 = polygon, 8 = multipoint.; x vector - vector of x coordinates.; y vector - vector of y coordinates.; z vector - optional vector of z coordinates.

shpObject = SHP_Create_Simple_Object(type,x vector,y vector[,z vector]);


myShpObject = SHP_Create_Simple_Object(1,-66 -67 -65.5,43 44 45.6,1 2 3.);

SHP_Write_Object

This command writes a shape object to a shape file.

There are 3 parameters:: shphandle - The SHP handle of the shp file to use.; shapeindex - index of the shape to write. Use -1 to create a new entry.; shpobject - Handle to the shape object that is to be written.

SHP_Write_Object(ShapeHandle,Shapeindex,ShapeObject);


SHP_Write_Object(shphdl,-1,myShpObj);

SHP_Read_Object

This command reads a shape object from a shape file into memory. The object returned is an enclosed vector with 18 elements.

The elements of the returned object are:
  object[1] = nSHPType
  object[2] = nShapeId
  object[3] = nParts
  object[4] = panPartStart integer vector
  object[5] = panPartType integer vector
  object[6] = nVertices
  object[7] = padfX double vector
  object[8] = padfY double vector
  object[9] = padfZ double vector
  object[10] = padfM double vector
  object[11] = dfXMin
  object[12] = dfYMin
  object[13] = dfZMin
  object[14] = dfMMin
  object[15] = dfXMax
  object[16] = dfYMax
  object[17] = dfZMax
  object[18] = dfMMax

There are 2 parameters:: shphandle - The SHP handle of the shp file to use.; shapeindex - index of the shape to read.

SHP_Read_Object(ShapeHandle,Shapeindex);


myObj = SHP_Read_Object(shphdl,0);

SHP_Get_Info

This command reads summary info from a shape file into memory. The object returned is an enclosed vector with 4 elements.

The elements of the returned object are:
  object[1] = number of entities
  object[2] = Shapefile type
  object[3] = vector of 4 values containing the minimum values for x,y,z and m
  object[4] = vector of 4 values containing the maximum values for x,y,z and m

There is 1 parameter:: shphandle - The SHP handle of the shp file to use.

SHP_Get_Info(ShapeHandle);


myInfo = SHP_Get_Info(shphdl);

ACON Home/Topics | Commands

Last Modified : 2005-11-14