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")
"EID" "X" "Y" "Detections" "Transmitter"
"1" 1 -155.932 19.482 63 782
"2" 2 -155.934 19.4779 1 782
PROJCS["NAD_1983_UTM_Zone_4N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-159.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
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