Fixing vertical and horizontal axes in R

Thanks, Shane, but that is precisely my problem. The final graph will not
be the default windows size and I want to
    a) nominate the overall height & width, and
    b) enforce the equal scales on the x and y axes.

My code currently looks like this:

# Generate image plot 2:
#-----------------------
fn <- "SpeciesRateLevels11F.jpg"
jpeg(fn, width=600, height=700)
zmeshR <- matrix(zmeshR,ng,ng)
image(xgrid,ygrid,zmeshR,bty="l",xlab="Easting",ylab="Northing",
      col=zz.colors,  xlim=c(xx1, xx2), ylim=c(yy1, yy2),
      main="Estimated number of native species /.01 ha")
points(x,y,col="red",cex=0.7)
lines(Jboundary[,1],Jboundary[,2],col="black",lwd=2)

b <- contourLines(xgrid,ygrid ,
             zmeshR, nlevels=11,
             levels = c(2, 4, 6, 8,10,12,14,16,18,20,22))
for (i in 1:11){
    lines(b[[i]], col="black", lwd=1)
}

Cheers,
Margaret Donald


On 12 May 2016 at 14:02, Shane Baylis <shane.m.baylis at gmail.com> wrote:

Hi Margaret,

It sounds like you're after eqscplot(), in package MASS. The overall size
can be set as for any plot window, but note that if you scale the plot by
dragging the limits of the plot window (or similar), the plot will need to
be re-generated after scaling the window to ensure that equal-scale is
maintained.

https://stat.ethz.ch/R-manual/R-devel/library/MASS/html/eqscplot.html

Hope that helps,

 Shane Baylis

On 12/05/16 13:13, Margaret Donald wrote:

I have a figure which uses the same measurement units both vertically and
horizontally. I need the interval representing 20 m to be identical for
both the x and y axes.  How do I specify this? And at the same time
dictate
the size of the overall graph which is being saved as a jpeg.


Regards,
Margaret Donald