R help - Aug 2014 - ggplot2: how to jitter spaghetti plot so slopes are preserved

Hi,

Suppose I have a the data frame given by:
> dput(toy.df)
structure(list(id = c(1, 2, 1, 2), time = c(1L, 1L, 2L, 2L),
    value = c(1, 2, 2, 3)), .Names = c("id", "time",
"value"), row.names = c(NA,
4L), class = "data.frame")

that is:
> toy.df
  id time value
1  1    1     1
2  2    1     2
3  1    2     2
4  2    2     3

I can create a "spaghetti" plot with the
command:
> ggplot(toy.df,aes(x=time,y=value,group=id,color=factor(id))) + geom_line()
What I'd like to be able to do is jitter the lines themselves by
translation so that their slopes are preserved, but so far my attempts
to jitter -- within ggplot, as opposed to first jittering toy.df by
hand -- seem to always jitter the two points for a given id
independently, and thus change the slopes.

I'd be grateful for any guidance!

Thanks,
David

Do the jittering yourself before you give the data to ggplot. 
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On August 20, 2014 4:56:04 PM PDT, David Romano <dromano at stanford.edu>
wrote:
>Hi,
>
>Suppose I have a the data frame given by:
>> dput(toy.df)
>structure(list(id = c(1, 2, 1, 2), time = c(1L, 1L, 2L, 2L),
>value = c(1, 2, 2, 3)), .Names = c("id", "time",
"value"), row.names >c(NA,
>4L), class = "data.frame")
>
>that is:
>> toy.df
>  id time value
>1  1    1     1
>2  2    1     2
>3  1    2     2
>4  2    2     3
>
>I can create a "spaghetti" plot with the command:
>> ggplot(toy.df,aes(x=time,y=value,group=id,color=factor(id))) +
>geom_line()
>
>What I'd like to be able to do is jitter the lines themselves by
>translation so that their slopes are preserved, but so far my attempts
>to jitter -- within ggplot, as opposed to first jittering toy.df by
>hand -- seem to always jitter the two points for a given id
>independently, and thus change the slopes.
>
>I'd be grateful for any guidance!
>
>Thanks,
>David
>
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