[R-sig-eco] Fixing vertical and horizontal axes in R

[Marc Taylor]

Hi Margaret,

Here is an example of scaling your figure based on the extension of the
axes. The margins are added as additional space beyond that scaling (here
in inches with par(mai=...) ). Having the additional argument asp=1 will
maintain the same aspect ration for both axes:

DIMS <- dim(volcano)
DIMS
fig.width <- 6
fig.height <- fig.width * (DIMS[2]/DIMS[1])
fig.height
MAI <- c(1,1,0.1,0.1) # margins in inches
fig.width <- fig.width + sum(OMI[c(2,4)]) # final figure width
fig.height <- fig.height + sum(OMI[c(1,3)]) # final figure height

jpeg("volcano.jpeg", width = fig.width, height = fig.height, units="in",
res=400)
op <- par(mai=MAI)
image(x=seq(nrow(volcano)), y=seq(ncol(volcano)), z=volcano, asp=1)
abline(v=seq(0, nrow(volcano), by=5), col=8, lty=3, lwd=0.75)
abline(h=seq(0, ncol(volcano), by=5), col=8, lty=3, lwd=0.75)
par(op)
dev.off()

Cheers,
Marc

On Thu, May 12, 2016 at 8:51 AM, Shane Baylis <shane.m.baylis at gmail.com>
wrote:

> Hi Margaret,
>
> eqscplot() can handle this scenario. Can you try:
>
> fn <- "SpeciesRateLevels11F.jpg"
> jpeg(fn, width = 600, height = 700)
> zmeshR <- matrix(zmeshR,ng,ng)
> eqscplot(x = x, y = y, type = "n", xlab = "Easting", ylab = "Northing",
>                main = "Estimated number of native species / .01 ha")
> image(xgrid,ygrid,zmeshR,bty="l",
>        col=zz.colors,
>        add = TRUE)
> 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)
> }
>
> In this case the limits of the plot will be set in terms of x and/or y,
> rather than xgrid and ygrid. If you need to include more of the
> background that was generated in your original image() call, you can use
> dummy x and y variables in the eqscplot() call, so that the whole
> image() area falls between their minimum and maximum.
>
> Cheers,
>
>   Shane
>
>
>
> On 12/05/16 15:55, Margaret Donald wrote:
> > 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
> > <mailto: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
> >
> >
> >
> >
> >     _______________________________________________
> >     R-sig-ecology mailing list
> >     R-sig-ecology at r-project.org <mailto:R-sig-ecology at r-project.org>
> >     https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
> >
> >
> >
> >
> > --
> > Margaret Donald BA (Hon), M. App Stat, Ph.D, AStat
> > Statistician, Anne Clements & Associates
>
>
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>
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