[R] expression exponent labeling

[Peter Ehlers]

On 2013-03-13 06:37, Gerrit Eichner wrote:
> Hi, Berry,
>
> I think
>
>> for(i in -8:-3) axis(1, i, substitute(10^j, list( j = i)))
>
> achieves what you want.
>
>    Regards --  Gerrit

Here's another (really no different) solution:

  for(i in -8:-3) axis(1, i, bquote(10^.(i)))

For more flexibility, if you need to do this a lot, you could
create an "expression" vector:

  x <- -8:-3
  z <- vector("expression", 6)
  for(i in 1:6) z[[i]] <- bquote(10^.(x[i]))
  axis(1, x, z)

Peter Ehlers

>
> On Wed, 13 Mar 2013, Berry Boessenkool wrote:
>
>>
>>
>> Hi all,
>>
>> I want to label an axis with exponents, but can't get it done with expression.
>> Any hints would be very welcome!
>>
>> # simulated data, somewhat similarly distributed to my real data:
>> set.seed(12); d <- rbeta(1e6, 0.2,2)*150 ; d <- d[d>1e-8]
>> hist( d  , breaks=100)
>> # now on a logarithmically scaled axis:
>> hist(log10(d), breaks=100, xaxt="n")
>> abline(v= log10(1:10*10^rep(-9:3, each=10)), col="darkgrey" ); box()
>> hist(log10(d), breaks=100, col="forestgreen", add=T)
>> axis(1, log10(1:10*10^rep(-9:3, each=10)), labels=F)
>> axis(1, -2:2, format(10^(-2:2), scient=3, drop0trailing=T) )
>> # the labels with lower values should be in the form of 10^x:
>> axis(1, -8:-3, expression( 10^(-8:-3)) )# doesn't work, because expression returns only one output
>> for(i in -8:-3) axis(1, i, expression(10^i)  ) # writes i at all locations
>>
>> expression does exactly what it should, but I want something different here...
>> I've tried I(10^i) instead, but that's not right either.
>>
>> Thanks ahead,
>> Berry
>>