PROSAGA码农传奇-模型可视化-R使用ggmap对象覆盖geom

<div class =“post-text”itemprop =“text”>
  <P>
    shapefile使用的坐标系不是lat-lon。您应该在将其转换为数据帧之前对其进行转换
     <code>
      ggplot
    </code>
    。以下作品：
  </p>
   <pre>
    <code>
      shpfile <- spTransform(shpfile, "+init=epsg:4326") # transform coordinates
tidydta2 <- tidy(shpfile, group=group)

wisc <- get_map(location = c(lon= -89.75, lat=44.75), zoom=7)

ggmap(wisc) +
  geom_polygon(aes(x=long, y=lat, group=group), 
               data=tidydta2, 
               color="dark red", alpha=.2, size=.2)

</code>
  </pre>
  <P>
    <a href="https://i.stack.imgur.com/32NK7.png" rel="nofollow noreferrer">
      <img src =“https://i.stack.imgur.com/32NK7.png”alt =“plot”/>
    </A>
  </p>
  <P>
    为了将来参考，请通过将数据框打印到带有可见x / y轴标签的控制台/绘图来检查坐标值。如果数字与背景地图的边界框的数字大不相同（例如7e + 05与47），则可能需要进行一些转换。例如。：
  </p>
   <pre>
    <code>
      > head(tidydta) # coordinate values of dataframe created from original shapefile
# A tibble: 6 x 7
     long     lat order hole  piece group id   
    <dbl>   <dbl> <int> <lgl> <chr> <chr> <chr>
1 699813. 246227.     1 FALSE 1     0.1   0    
2 699794. 246082.     2 FALSE 1     0.1   0    
3 699790. 246007.     3 FALSE 1     0.1   0    
4 699776. 246001.     4 FALSE 1     0.1   0    
5 699764. 245943.     5 FALSE 1     0.1   0    
6 699760. 245939.     6 FALSE 1     0.1   0

> head(tidydta2) # coordinate values of dataframe created from transformed shapefile
# A tibble: 6 x 7
   long   lat order hole  piece group id   
  <dbl> <dbl> <int> <lgl> <chr> <chr> <chr>
1 -87.8  42.7     1 FALSE 1     0.1   0    
2 -87.8  42.7     2 FALSE 1     0.1   0    
3 -87.8  42.7     3 FALSE 1     0.1   0    
4 -87.8  42.7     4 FALSE 1     0.1   0    
5 -87.8  42.7     5 FALSE 1     0.1   0    
6 -87.8  42.7     6 FALSE 1     0.1   0

> attr(wisc, "bb") # bounding box of background map
# A tibble: 1 x 4
  ll.lat ll.lon ur.lat ur.lon
   <dbl>  <dbl>  <dbl>  <dbl>
1   42.2  -93.3   47.2  -86.2

# look at the axis values; don't use theme_void until you've checked them
cowplot::plot_grid(
  ggplot() +
    geom_polygon(aes(x=long, y=lat, group=group), 
                 data=tidydta, 
                 color="dark red", alpha=.2, size=.2),
  ggplot() +
    geom_polygon(aes(x=long, y=lat, group=group), 
                 data=tidydta2, 
                 color="dark red", alpha=.2, size=.2),
  labels = c("Original", "Transformed")
)

</code>
  </pre>
  <P>
    <a href="https://i.stack.imgur.com/7TZ5b.png" rel="nofollow noreferrer">
      <img src =“https://i.stack.imgur.com/7TZ5b.png”alt =“比较”/>
    </A>
  </p>
</DIV>

R使用ggmap对象覆盖geom_polygon，进行空间文件转换