[R] Logarithmic axis

[Julian Burgos]

Hey John,

You can do simply

plot(reizstaerke, kennlinie1, ylim=c(0, max(kennlinie1, 
kennlinie2)),log="x")

but if you want to fine tune where the tick marks are, you can do it "by 
hand".

kennlinie1 <-  c(8.0746909, 3.9916973, 9.9789444, 19.962869);
kennlinie2 <-  c(6.0994206, 8.9661081, 19.924883, 31.879496);
reizstaerke <- c(76, 92, 108, 124);
plot(log10(reizstaerke), kennlinie1, ylim=c(0, max(kennlinie1, 
kennlinie2)),axes=F)
box()
axis(1,at=log10(seq(75,125,by=5)),label=seq(75,125,by=5))
axis(2)

The obvious reason that you are getting a plot with a single 100 and 
nothing else is that the range of the values in the reizstaerke vector 
is away from 10 and from 1000.  If you really want to have the log scale 
in the way you described, you could do something like this:

plot(log10(reizstaerke), kennlinie1, ylim=c(0, max(kennlinie1, 
kennlinie2)),axes=F,xlim=log10(c(1,1000)))
box()
axis(1,at=log10(c(1,10,100,1000)),label=c(1,10,100,1000))
axis(2)

Julian


John Wiedenhoeft wrote:
> Hi there,
> 
> I guess this must be a standard issue, but I'm starting to go crazy with it. I 
> simply want a plot with the x axis being logarithmic, having labels 1, 10, 
> 100..., and ten unlabelled ticks between each of them - just as they 
> introduce logarithmic axis at school. I've played around a bit with log="x", 
> xlog=T (where exactly is the difference here?), xaxp, and xaxt (unfortunately 
> xaxt="l" isn't implemented). The best I get is a plot with an axis having a 
> single 100 and nothing else...
> 
> here is what I've tried:
> 
> pdf(file="kennlinien.pdf");
> par(log="x", xlog=TRUE);
> kennlinie1 <-  c(8.0746909, 3.9916973, 9.9789444, 19.962869);
> kennlinie2 <-  c(6.0994206, 8.9661081, 19.924883, 31.879496);
> reizstaerke <- c(76, 92, 108, 124);
> #plot(reizstaerke, kennlinie1, ylim=c(0, max(kennlinie1, kennlinie2)), 
> xlim=c(0, max(reizstaerke)), log="x", xlog=TRUE, xaxp=c(1, 2, 1), type="b");
> #plot(reizstaerke, kennlinie1, type="b", log="x", xlog=TRUE, xaxp=c(1, 2, 3));
> plot(reizstaerke, kennlinie1, type="b",usr=c(min(reizstaerke), 
> max(reizstaerke), min(kennlinie1, kennlinie2), max(kennlinie1, kennlinie2)), 
> log="x", xlog=TRUE, xaxp=c(1, 2, 3));
> #points(reizstaerke, kennlinie2, xlog=TRUE, xaxp=c(1, 3, 3), type="b");
> dev.off();
> 
> Certainly I've missed something, but I can't figure it out.
> 
> Any help appreciated,
> Cheers, 
> John
> 
> 
> 
> platform       i486-pc-linux-gnu
> arch           i486
> os             linux-gnu
> system         i486, linux-gnu
> status
> major          2
> minor          4.1
> year           2006
> month          12
> day            18
> svn rev        40228
> language       R
> version.string R version 2.4.1 (2006-12-18)
> 
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