[R] Bubble plot on shapefile - projection issues?

[t c]

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")



      
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