# [R] lattice: how to use a log scale on the x-axis with the bwplot function

Bert Gunter bgunter@4567 @end|ng |rom gm@||@com
Sat Dec 10 19:20:37 CET 2022

```If Deepayan's suggestion does not suit and especially *if* I understand
what you want to do correctly, then it seems to me that it is
straightforward to create the groups and group labels manually:

## in verbose detail to hopefully improve clarity
set.seed(123)  ## for reprex
y <- runif(40,min=0, max= 10)  ##*small* reprex
## cut y into 5 equally spaced groups labeled by log10 of the center
## of the intervals
yrng <- range(y)
eps <- .0001*c(-1,1)*diff(yrng) ## see ?cut
yrng <-yrng + eps
delta <- diff(yrng)/5 # 5 = number of intervals
brks <- seq(yrng, yrng,length.out =6)
labs <- round(log10(brks[-1] - delta/2), 2) ## log10 (centers)
groups <- cut(y,breaks = brks,
labels = paste0('10^',labs))
# creating the dataframe for the lattice functions
DF <- data.frame( y = y, groups = groups)

bwplot( y ~ groups
, data=DF
, scales = list(
y = list(log=T)
),
)

## Of course, ignore if I have misunderstood.

Cheers,
Bert

On Sat, Dec 10, 2022 at 8:03 AM Deepayan Sarkar <deepayan.sarkar using gmail.com>
wrote:

> Log-scales for the "factor" variable in bwplot() is not allowed.
>
> You could, however, use the panel function panel.bwplot() with
> xyplot(num ~ num). The potential problem with that is the box widths,
> which panel.bwplot() will not know how to compute.
>
> See if the following gives you a reasonable starting point:
>
> DF <- within(DF, m <- tapply(y, groups, mean))
> xyplot(y ~ m, DF, scales = list(log = TRUE),
>        panel = panel.bwplot, horizontal = FALSE,
>        box.width = .0001)
>
> Best,
> -Deepayan
>
> On Sat, Dec 10, 2022 at 7:46 PM Laurent Rhelp <LaurentRHelp using free.fr>
> wrote:
> >
> > Dear R-Help list,
> >
> >     I would like to use bwplot from the lattice package with a log scale
> > both on
> > the x-axis and the y-axis but I do not know how to do that because I do
> > not know
> > how to change the factor x-axis in a numeric x-axis.
> >
> >   Here is my example:
> >
> >
> > library(lattice)
> >
> > # the mock data
> > y <- runif(100000,min=0, max=500)
> > x <- seq(0,500,length=length(y))
> > # I cut the x variable to create a factor variable in order to calculate
> > the boxes
> > groups <- cut(x,10,ordered_result = TRUE)
> > # creating the dataframe for the lattice functions
> > DF <- data.frame( x= x , y = y, groups = groups)
> >
> >
> > ## ok for xyplot
> > xyplot(   y ~ x
> >            , data=DF
> >            , scales = list(
> >              y = list(log=T)
> >              , x = list(log=T)
> >
> >            )
> > )
> >
> > ## ok for bwplot with the log scale for the y-axis
> > bwplot( y ~ groups
> >            , data=DF
> >            , scales = list(
> >              y = list(log=T)
> >              #     , x = list(log=T)
> >
> >            )
> > )
> >
> >
> >
> > ## Non ok for bwplot with the log scale for the x-axis
> > bwplot( y ~ groups
> >          , data=DF
> >          , scales = list(
> >                y = list(log=T)
> >              , x = list(log=T)
> >
> >          )
> > )
> > which gives an error because the x-axis is a factor, I would like to
> > replace it
> > for the display by the meddle of every class for example and put a log
> > scale on the x-axis.
> >
> > Thank you for your help
> > Best regards
> > Laurent
> >
> >
> >
> > --
> > Cet e-mail a été vérifié par le logiciel antivirus d'Avast.
> > www.avast.com
> >
> > ______________________________________________
> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help