PROSAGA码农传奇-时空索引-如何有效地规划河流？

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  <P>
    如果您经常使用shapefile，geom_path和geom_polygon会提供您需要的一切。在最近的版本中，ggplot直接处理空间对象，因此不需要使用强化和合并（可能是在代码中花费更多时间的步骤）。这是一个使用的例子
    <a href="ftp://geoftp.ibge.gov.br/organizacao_do_territorio/malhas_territoriais/malhas_municipais/municipio_2017/Brasil/BR/br_unidades_da_federacao.zip" rel="nofollow noreferrer">
      来自IBGE的巴西联邦单位的形状文件
    </A>
     作为基本地图：
  </p>
   <pre>
    <code>
      shapeUFs <- readOGR('.', 'BRUFE250GC_SIR')
shapeHid <- readOGR('.', 'PrincipaisRiosDoBrasil')

ggplot(shapeUFs, aes(long, lat, group = group)) +
  geom_polygon(fill = 'gray90', color = 'black') +
  geom_path(data = shapeHid, color = 'steelblue2') +
  coord_map() + theme_void()

</code>
  </pre>
  <P>
    <a href="https://i.stack.imgur.com/II51g.png" rel="nofollow noreferrer">
      <img src =“https://i.stack.imgur.com/II51g.png”alt =“在此处输入图片说明”/>
    </A>
  </p>
  <P>
    性能将受到形状大小（由特征数量和细节级别决定）的影响，而不是您在ggplot中使用的几何形状。您可以使用rgeos :: gSimplify来减少空间多边形/线对象中的顶点数。您还可以直接在地图上绘制点：
  </p>
   <pre>
    <code>
      # Simplifying the geometry of the federative units
shapeUFs.s <- rgeos::gSimplify(shapeUFs, .05, TRUE)

# Storing map in an object
riversMap <- ggplot(shapeUFs.s, aes(long, lat)) +
  geom_polygon(aes(group = group), fill = 'gray90', color = 'black') +
  geom_path(data = shapeHid, aes(group = group), color = 'steelblue2') +
  coord_map() + theme_void()

# Sampling 20 cities in Brazil
brMunics <- read.csv('https://raw.githubusercontent.com/kelvins/Municipios-Brasileiros/master/Municipios_Brasileiros.csv')
Munics <- brMunics[sample(nrow(brMunics), 20), ]

# Plotting points over the map
riversMap + geom_point(data = Munics, aes(Longitude, Latitude), color = 'red')

# If your data already have the coordinates named 'lat' and 'long',
# you can skip aes(Longitude, Latitude):
names(Munics)[6:7] <- c('lat','long')
riversMap + geom_point(data = Munics, color = 'red')

</code>
  </pre>
  <P>
    <a href="https://i.stack.imgur.com/Yb6il.png" rel="nofollow noreferrer">
      <img src =“https://i.stack.imgur.com/Yb6il.png”alt =“在此处输入图片说明”/>
    </A>
  </p>
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