[R-sig-Geo] rgdal writeOGR - clipping variable names

[James Rooney]

Hi all,

I am using writeOGR to save ESRI shapefiles after a ton of processing. Typical warning message I get is as follows:

> writeOGR(ED, "/Users/jrooney/Documents/My Projects/ALS Spatial - Advanced/Irish Data/Processed Data/", layer="ED.cluster",driver="ESRI Shapefile",overwrite=T)
Warning message:
In writeOGR(ED, "/Users/jrooney/Documents/My Projects/ALS Spatial - Advanced/Irish Data/Processed Data/",  :
  Field names abbreviated for ESRI Shapefile driver

Now it has been doing this all along. But lately it has changed. For example - I frequently use the column id "GEOGID" as I've inherited it somewhere along the line from some dataset I got somewhere.
Until recently it was happily saving this column name in its entireity. Lately, for some mystery reason it is not saving it fully and only saving 5 letters - "GEOGI". This, as you can imagine is causing me troubles.

Anyhow - why are field names so short for ESRI shapfiles and why does it sometimes accept 6 letter fields and other times not ? It would be great if it would allow longer field names, as 5 letters is not alot when you have over 100 variables - it gets confusing even when you use codes.

Many thanks,
James