Bubble plot on shapefile - projection issues?

Dear R help list,

I am working on some data from a study on the habitat use and  
movement patterns of fish using a marine protected area in Hawaii.   
We have a number of acoustic receivers in a MPA, and any time a  
tagged fish passes within range it records the date and time of  
detection.  I am trying to make bubble plots showing the number of  
detections for each fish at each receiver.  I have been able to get  
it to work using a map generated from GSHHS data (Global Self- 
consistent, Hierarchical, Highresolution Shoreline) but the map data  
is not of high enough resolution.  Instead I am trying to plot the  
data on a shapefile, but I can't find out how to project the  
shapefile correctly to match up with the data.  I know my shapefile  
is in NAD 1983 UTM Zone 4N and my data is in WSG84.  How do I change  
the projections to make them line up?  I tried mapproj but couldn't  
get it to work.  Any suggestions would be greatly appreciated.

My code is below.  I have also attached the shapefile and my data.

Thanks in advance for your help.

Aloha,

Tim




#Read ESRI shapefiles
library(maptools)
library (PBSmapping)
setwd("E:/Telemetry_research/Kealakekua Bay MPA study/R bubble plot")
hawaii.coast<- read.shape("coast_n83.shp")

#Read data and convert to event data
 mydat<-read.table("my.event", header=TRUE)
 my.event<-as.EventData(mydat,projection="LL")

#Calculate bubble size
 detects<-mydat$Detections
 max.symbol.size=10
 min.symbol.size=1
 bubble.size <- (detects-min(detects))/((max(detects)+.0001)- 
min(detects))*(max.symbol.size-min.symbol.size)+min.symbol.size       
#Calculates bubble size as a range between min and max.  0.0001  
added to avoid division by zero if only one sample.

#Plot of all Hawaiii showing point data somewhere to the south.   
Needs projcting?
plot(hawaii.coast,xlab="Longitude",ylab="Latitude",main="Kealakekua  
Bay")
addPoints(my.event, pch=19 ,col="red",cex=500)



#Plot of location where point data should be
plot(hawaii.coast,xlim=c(820000, 824000), ylim=c(2154000,  
2158000),xlab="Longitude",ylab="Latitude",main="Kealakekua Bay")



< 
my.event><coast_n83.prj>______________________________________________
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