ArcGis 统计方法

from:http://blog.sina.com.cn/s/blog_4177d50b0100fjbg.html

概述

一般常用的统计功能例如：唯一字段统计、数据行数统计、数据值求和统计等。

1、基础统计（BaseStatistics）组件用来生成和报告统计结果。

2、IFrequencyStatistics接口提供对用来报告频率统计的成员的访 问。

3、IGenerateStatistics接口提供对用来生成统计结果的成员的访问。

4、IStatisticsResults提供对用来报告统计结果的成员的访问。

可访问的属性有Count,Sum,Maximum,Minimum,Meanm,StandardDeviation(标准差)

DataStatistics组件允许返回统计结果及单个字段的唯一值。组件创建后，用来分析的数据通过IDataStatistics::Cursor属性，以光标形式的传入。注意ICursor的对象只能使用一次，如果要获取多个结果，应当再次创建光标。IDataStatistics是数据统计组件中唯一的接口

1、IDataStatistics

属性

Cursor－－通过游标来生成统计表

Field－－要统计的字段

UniquueCount－－统计表中唯一值总数

Uniquues－－唯一值枚举

Statistics－－ IStatisticsResults对象，用于返回统计信息

2、IStatisticsResults

属性

Count－－值总数

Maximum －－最大值

Mean－－算术平均值

Minimum－－最小值

StandardDeviation－－标准差

Sum－－求和

示例：唯一字段统计，GeoDatabase没有提供DISTINCT这样的关键字进行唯一值查询，只有通过IDataStatistics::Uniquues方式来获取唯一值

public void IDataStatistics_Example(IFeatureClass featureClass)
    {
        ICursor cursor = (ICursor)featureClass.Search(null, false);

IDataStatistics dataStatistics = new DataStatisticsClass();
        dataStatistics.Field = "PIP_SIZE";

dataStatistics.Cursor = cursor;

//求唯一值

System.Collections.IEnumerator enumerator = dataStatistics.Uniquues;
        enumerator.Reset();

while (enumerator.MoveNext())
        {
            object myObject = enumerator.Current;
            Console.WriteLine("Value - {0}", myObject.ToString());

}

//求算术平均值

cursor = (ICursor)featureClass.Search(null, false);
        dataStatistics.Cursor = cursor;
        ESRI.ArcGIS.esriSystem.IStatisticsResults statisticsResults = dataStatistics.Statistics;
        Console.WriteLine("mean value - {0}", statisticsResults.Mean);

}

通过接口说明和示例可以看出，统计信息是基于数字字段的统计。

另外，关于查询与统计接口，还有IQueryDef、IQueryFilterDefinition、ITable等。例子如下：

//IQueryDef Example

public void IQueryDef_Example(IWorkspace workspace)

{
        IFeatureWorkspace featureWorkspace = (IFeatureWorkspace)workspace;
        //create query definition
        IQueryDef queryDef = featureWorkspace.CreateQueryDef();
        //provide list of tables to join
        queryDef.Tables = "datesjoin,dudatest";
        //retrieve the fields from all tables
        queryDef.SubFields = "sde.datesjoin.dt_field = sde.dudates.dt_field";
        //set up join
        queryDef.WhereClause = "datesjoin.dt_field = dudates.dt_field";

//Create FeatureDataset. Note the use of .OpenFeatureQuery.
        //The name "MyJoin" is the name of the restult of the query def and
        //is used in place of a feature class name.
        IFeatureDataset featureDataset = featureWorkspace.OpenFeatureQuery("MyJoin", queryDef);
        //open layer to test against
        IFeatureClassContainer featureClassContainer = (IFeatureClassContainer)featureDataset;
        IFeatureClass featureClass = featureClassContainer.get_ClassByName("MyJoin");

}

//IQueryFilterDefinition PostfixClause Example

public void IQueryFilterDefinition_PostfixClause_Example(IFeatureClass featureClass)
    {
        //this function uses the PostfixClause property to append an Order By clause to the query.
        IQueryFilter queryFilter = new QueryFilterClass();
        queryFilter.SubFields = "FULLNAME";
        queryFilter.WhereClause = "OBJECTID > 10";
        IQueryFilterDefinition queryFilterDefinition = (IQueryFilterDefinition)queryFilter;
        queryFilterDefinition.PostfixClause = "ORDER BY FULLNAME";
        IFeatureCursor featureCursor = featureClass.Search(queryFilter, true);
        int fieldIndex = featureCursor.FindField("FULLNAME");
        IFeature feature = featureCursor.NextFeature();
        while (feature != null)
        {
            Console.WriteLine("The value of the {0} field is {1)", featureCursor.Fields.get_Field(fieldIndex).Name, feature.get_Value(fieldIndex));
            feature = featureCursor.NextFeature();
        }
    }

//ITable Example

Public Void ITable_Example(IFeatureClass featureClass)

{

ITable pTable = featureClassas ITable;

Console.WriteLine("The Row Count is:{0}",pTable.RowCount.Tostring());

}