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

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[1], yrng[2],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 at 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 at 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



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