[R] ggplot2 used in a function - variable scope/environment

[Martin Rittner]

Hi Hadley,

that helps perfectly! The actual solution, given my former example, would be

mapping=aes(x=names(da)[1],y=c)

I read about aes_string() sometime, but I didn't realize it was the
solution to this problem... As often, PEBKAC!

Many Thanks!
Martin


hadley wickham wrote:
> Hi Martin,
> 
> Two comments:
> 
>  * ggplot always requires the data to be plotted to be stored in a
> data.frame, not the environment  - this makes it possible to (e.g.)
> save self contained plot objects - but that isn't the problem here,
> the problem is setting up the appropriate mapping
> 
>  * aes_string makes it easier to build up aesthetic mappings
> programmatically - aes_string(x = names(data)[1], y = names(data)[c])
> 
> Does that help?
> 
> Hadley
> 
> On Fri, Feb 15, 2008 at 2:21 PM, Martin Rittner
> <martin.rittner at thegeologician.net> wrote:
>> Hi everybody!
>>
>>  I'm trying to use ggplot2 to return a plot from a function (so I can add
>>  something or alter it then). Unfortunately, if I add a mapping to a
>>  layer in the function, the variable *name* is stored in the layer,
>>  rather than the variable's *value* - so that after the function returns
>>  the ggplot2-object, it doesn't plot because the variable don't exist in
>>  the environment calling the function.. e.g:
>>
>>  my function does something like:
>>
>>  getPlot<-function(da=NULL,...){
>>         #1st column holds x-values, others hold data series to plot...
>>         co<-as.character(names(da))
>>         co<-co[2:length(co)]
>>
>>         pl<-ggplot(data=da)
>>         pl<-pl+scale_y_log10()+scale_x_continuous()
>>         for(c in co){
>>                 pl<-pl+geom_line(x=da[[1]],y=da[[c]],mapping=aes(x=da[[1]],y=da[[c]]))
>>         }
>>
>>         return(pl)
>>  }
>>
>>  I need to add every layer separately, because I want to be able to
>>  explicitly define attributes for every data series (colour, size... e.g.
>>  highlight only two specific out of 10 series...).
>>
>>  Anyway, my problem is this:
>>
>>  d<-data.frame(x=seq(0.0,1.0,length=5),y1=rnorm(5),y2=rnorm(5))
>>  p<-getPlot(da=d)
>>  p
>>
>>  returns with
>>
>>  Error in data.frame(..., check.names = FALSE) :
>>    arguments imply differing number of rows: 0, 5
>>
>>  and the plot object contains:
>>
>>  Title:
>>  Labels:  x=, y=
>>  -----------------------------------
>>  Data:    x, y1, y2 [5x3]
>>  Mapping:
>>  Scales:  y,x -> y,x
>>  $margins
>>  [1] FALSE
>>
>>  $facets
>>  [1] ". ~ ."
>>
>>  -----------------------------------
>>  geom_line: (colour=black, size=1, linetype=1, x=NA, y=NA) + (x=c(0,
>>  0.25, 0.5, 0.75, 1), y=c(0.180036717548597, -0.369556903134046,
>>  -0.924474152821948, -2.40773640658189, 0.801471591443009))
>>  stat_sort: (...=) + (x=c(0, 0.25, 0.5, 0.75, 1), y=c(0.180036717548597,
>>  -0.369556903134046, -0.924474152821948, -2.40773640658189,
>>  0.801471591443009))
>>  position_identity: ()
>>  mapping: (x=da[[1]], y=da[[c]])
>>
>>  geom_line: (colour=black, size=1, linetype=1, x=NA, y=NA) + (x=c(0,
>>  0.25, 0.5, 0.75, 1), y=c(-1.59744511956184, -0.9333541477049,
>>  1.88697835844878, 0.921829569181679, -0.741077741846118))
>>  stat_sort: (...=) + (x=c(0, 0.25, 0.5, 0.75, 1), y=c(-1.59744511956184,
>>  -0.9333541477049, 1.88697835844878, 0.921829569181679, -0.741077741846118))
>>  position_identity: ()
>>  mapping: (x=da[[1]], y=da[[c]])
>>
>>  Note the mappings, they refer to "da" and "c" (defined in the function)
>>  which are not available in the calling environment. Any Idea how I can
>>  avoid the problem/paste the actual values in, like it did for the
>>  geometry and the statistics?
>>
>>  Thanks, Martin
>>
>>  ______________________________________________
>>  R-help at r-project.org mailing list
>>  https://stat.ethz.ch/mailman/listinfo/r-help
>>  PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>  and provide commented, minimal, self-contained, reproducible code.
>>
> 
> 
>