get_map 发生了什么？

我今天开始使用 get_map 向 googlemaps 发出大约 230 个地图请求，然后出现错误（丢失了原始错误）。我的第一个假设是我使用它超出了 api 的限制，但我尝试使用开放街道地图 api 作为源，我收到的错误消息仍然看起来像 get_map 正在使用 googlemaps。这是怎么回事？我重新启动了计算机并尝试重现该错误。当我访问源代码中列出的 url 时，我没有得到我的地图，而是得到一个小图像，看起来像是我检查了 api 使用情况。但我已将源设置为 osm。

> library(ggmap)
Loading required package: ggplot2
Warning message:
package ‘ggmap’ was built under R version 3.1.1 
Loading required package: sp
> get_map(source = "osm")
Error in download.file(url, destfile = destfile, quiet = !messaging, mode = "wb") : 
  cannot open URL 'http://maps.googleapis.com/maps/api/staticmap?center=29.763284,-95.363271&zoom=10&size=%20640x640&maptype=terrain&sensor=false'
In addition: Warning messages:
1: package ‘sp’ was built under R version 3.1.1 
2: In download.file(url, destfile = destfile, quiet = !messaging, mode = "wb") :
  cannot open: HTTP status was '403 Forbidden'
> detach(sp)
Error in detach(sp) : invalid 'name' argument
> detach("sp")
Error in detach("sp") : invalid 'name' argument
> get_map(source = "osm")
Error in download.file(url, destfile = destfile, quiet = !messaging, mode = "wb") : 
  cannot open URL 'http://maps.googleapis.com/maps/api/staticmap?center=29.763284,-95.363271&zoom=10&size=%20640x640&maptype=terrain&sensor=false'
In addition: Warning message:
In download.file(url, destfile = destfile, quiet = !messaging, mode = "wb") :
  cannot open: HTTP status was '403 Forbidden'

这是我为获取地图图像而设置的原始循环。

for(i in seq(levels(named_trails$TRAIL_NAME))) {
one_trail <- named_trails[which(named_trails$TRAIL_NAME == levels(named_trails$TRAIL_NAME)[i]),]
map_center <- c(min(one_trail$long) - 0.02, min(one_trail$lat) - 0.02, max(one_trail$long) + 0.02, max(one_trail$lat) + 0.02)
anc_map <- get_map("anchorage, AK", source = "stamen")
p <- ggmap(anc_map) +
    geom_line(data = one_trail, aes(x = long, y = lat, color = TRAIL_NAME)) +
    ggtitle(levels(named_trails$TRAIL_NAME)[i]) +
    theme(legend.position="none")
ggsave(paste(i, ".png", sep = ""))
Sys.sleep(4)
}

视窗 7 x86 R 3.1.0 Rstudio版本0.98.932

问题似乎是当您指定source="osm"但位置类型不是边界框，然后它会调用get_googlemap在从 openstreetmap 中提取地图之前获取纬度/经度位置。因此，您需要确保在使用时传入长度为 4 且带有纬度/经度坐标的向量source="osm"以避免对 Google 地图 API 的任何调用。看来 OSM 无法自行将“锚地，AK”之类的内容转换为经度和纬度值。