[R] removing a specific number of digist from a character string

[Kim Milferstedt]

Hello,

I would like to remove the last 8 digists of character strings in a 
vector. Below I added a couple of elements from that vector.

I have a problem defining a pattern to replace the digits using for 
example "sub". Removing the ".tif" part works fine using 
sub('.tif',"",x), but how do I get rid of the four preceding digits?

Thanks for your help,

Kim

Input:
[3988] 
"060907_17_3_5_1_1_2909.tif"   "060907_17_3_5_2_1_2910.tif" 
"060907_17_3_5_3_1_2911.tif"
[3991] 
"060907_17_3_5_4_1_2912.tif"   "060907_17_3_5_5_1_2913.tif" 
"060907_17_3_5_6_1_2914.tif"

Desired output:
[3988] "060907_17_3_5_1_1_"   "060907_17_3_5_2_1_"   "060907_17_3_5_3_1_"
[3991] "060907_17_3_5_4_1_"   "060907_17_3_5_5_1_"   "060907_17_3_5_6_1_"

__________________________________________

Kim Milferstedt
University of Illinois at Urbana-Champaign
Department of Civil and Environmental Engineering
4125 Newmark Civil Engineering Laboratory
205 North Mathews Avenue MC-250
Urbana, IL 61801
USA
phone: (001) 217 333-9663
fax: (001) 217 333-6968
email: milferst at uiuc.edu
http://cee.uiuc.edu/research/morgenroth