linux - readChar 错误(con，5L，useBytes = TRUE): cannot open the connection

Question

“mow.R”现在包含:

library(RgoogleMaps);
png(filename="RgoogleMaps-package_%03d_med.png", width=480, height=480);

MyMap <- GetMap(markers='&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc', destfile="MyTile1.png");

这会导致以下新错误:

> source('mow.R')
[1] "Note that when center and zoom are not specified, no meta information on the map tile can be stored. This basically means that R cannot compute proper coordinates. You can still download the map tile and view it in R but overlays are not possible. Do you want to proceed ? (y/n)"
y
[1] "&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc"
[1] "http://maps.google.com/maps/api/staticmap?size=640x640&maptype=terrain&format=png32&sensor=true&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc"

Error in readChar(con, 5L, useBytes = TRUE) : cannot open the connection
In addition: Warning message:
In readChar(con, 5L, useBytes = TRUE) :
  cannot open compressed file 'MyTile1.png.rda', probable reason 'No such file or directory'
> 

纠正这个错误的方法是什么？

R 版本 2.15.1
RgoogleMaps 版本 1.2.0

---

> sessionInfo() 
R version 2.15.1 (2012-06-22)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=C                 LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] RgoogleMaps_1.2.0 png_0.1-4        
> 

Answer 1

已解决。这是工作代码:

library(RgoogleMaps);
png(filename="Rg.png", width=480, height=480);


lat    = c(40.702147,40.718217,40.711614);
lon    = c(-74.012318,-74.015794,-73.998284);
center = c(mean(lat), mean(lon));
zoom <- min(MaxZoom(range(lat), range(lon)));

MyMap <- GetMap(center=center, zoom=zoom, markers='&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc', destfile="My.png");

tmp <- PlotOnStaticMap(MyMap,lat=c(40.702147,40.711614,40.718217),lon=c(-74.015794,-74.012318,-73.998284),cex=1.5,pch=20,col=c('red', 'blue', 'green'),add=F);

dev.off();

这导致:

dd@linux-y3pi:~/RTest> ls
new.R

dd@linux-y3pi:~/RTest> R

R version 2.15.1 (2012-06-22) -- "Roasted Marshmallows"
Copyright (C) 2012 The R Foundation for Statistical Computing
ISBN 3-900051-07-0
Platform: x86_64-unknown-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

  Natural language support but running in an English locale

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

[Previously saved workspace restored]

> source('new.R')
Loading required package: png
[1] "&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc"
[1] "http://maps.google.com/maps/api/staticmap?center=40.7106593333333,-74.0087986666667&zoom=15&size=640x640&maptype=terrain&format=png32&sensor=true&40.702147,-74.015794,blues%7C40.711614,-74.012318,greeng%7C40.718217,-73.998284,redc"
> q()
Save workspace image? [y/n/c]: y

dd@linux-y3pi:~/RTest> ls
My.png  My.png.rda  new.R  Rg.png

dd@linux-y3pi:~/RTest>