Using the maptools function "map2poly" I have created a map/polylist object
- a map of the Great Lakes. My goal is to passively plot additional data on
this map. Unfortunately I am not able to change (distort) the relative scale
of the axes for the map, and so the sample points do not line up correctly
on the map.
In the code below, notice that I have set the same axis ranges on each plot
for x (longitude) and y (latitude), and yet it has no effect on the map
plot. For example, if I stretch the plot window vertically, the y data
spread out accordingly, but the map remains undistorted. No matter how much
I try to stretch the y axis, the y:x ratio scale remains 1:1. How do I force
the map to fit the ranges that I set like I can for the data plot?
*# make the map object "lakes"
tmp <- read.shape('D:/R/great lakes map/grtlakes/grtlakes')
lakes <- Map2poly(tmp)
# read sample location data to be plotted on map
locs <- read.table("locs.csv", header=TRUE, sep=",", na.strings="NA",
dec=".", strip.white=TRUE)
# plot map, then sample locations
plot(lakes,xlim=range(-76,-93), ylim=range(40,50))
par(new=TRUE) # put next plot on same graph
plot(LATITUDE~LONGITUDE, data=locs,xlim=range(-76,-93),ylim=range(40,50))
box()*
Thank you for any help - Euan.
Euan D. Reavie
Center for Water and the Environment
Natural Resources Research Institute
University of Minnesota Duluth
1900 East Camp Street, Ely, MN 55731
email ereavie *at sign* nrri.umn.edu
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