[R] geom_bar with missing data in package ggplot

[Aidan Corcoran]

Hi Dennis,

that does exactly what I needed, and the treatment of missing values
is really useful.

thanks for your help.
Aidan

On Wed, Nov 16, 2011 at 12:22 PM, Dennis Murphy <djmuser at gmail.com> wrote:
> Hi:
>
> Here's one way, but it puts the two countries side by side rather than
> stacked (I'm not a big fan of stacked bar charts except in certain
> contexts). The first version uses the original data, but one can see
> immediately that there is no distinction between NA and 0:
>
> ggplot(g, aes(x = Date, y = value, fill = var2)) +
>    geom_bar(position = 'dodge', stat = 'identity') +
>    facet_wrap(~ variable, nrow = 1) +
>    scale_fill_manual('Country', breaks = levels(g$var2),
>                                 values = c('red', 'blue')) +
>    opts(legend.position = c(0.87, 0.88),
>         legend.background = theme_rect(fill = 'white'))
>
> To compensate, I copied the data to a new object g2 and imputed a
> small negative value to replace the zero:
>
> g2 <- g
> g2$value[8] <- -0.01
> ggplot(g2, aes(x = Date, y = value, fill = var2)) +
>    geom_bar(position = 'dodge', stat = 'identity') +
>    facet_wrap(~ variable, nrow = 1) +
>    scale_fill_manual('Country', breaks = levels(g2$var2),
>                                 values = c('red', 'blue')) +
>    opts(legend.position = c(0.87, 0.88),
>         legend.background = theme_rect(fill = 'white'))
>
> An additional improvement could be made by keeping the original data
> and adding some text that indicates where the NAs reside; to do this,
> we need to offset the date a bit to decently locate the text:
>
> ggplot(g, aes(x = Date, y = value, fill = var2)) +
>    geom_bar(position = 'dodge', stat = 'identity') +
>    facet_wrap(~ variable, nrow = 1) +
>    scale_fill_manual('Country', breaks = levels(g$var2),
>                                 values = c('red', 'blue')) +
>    geom_text(aes(x = as.Date('2001-3-31'), y = 1, label = 'NA'),
>               size = 6) +
>    opts(legend.position = c(0.87, 0.88),
>         legend.background = theme_rect(fill = 'white'))
>
> HTH,
> Dennis
>
>
>
> On Wed, Nov 16, 2011 at 1:55 AM, Aidan Corcoran
> <aidan.corcoran11 at gmail.com> wrote:
>> Dear all,
>>
>> I was hoping someone could help with a ggplot question. I would like
>> to generate a faceted bar chart, but missing data are causing
>> problems.
>>
>> g<-structure(list(Date = structure(c(11322, 11687, 12052, 11322,
>> 11687, 12052, 11322, 11687, 12052, 11322, 11687, 12052), class = "Date"),
>>    variable = c("Govt Revenues to GDP", "Govt Revenues to GDP",
>>    "Govt Revenues to GDP", "Govt Revenues to GDP", "Govt Revenues to GDP",
>>    "Govt Revenues to GDP", "Structural Budget Position", "Structural
>> Budget Position",
>>    "Structural Budget Position", "Structural Budget Position",
>>    "Structural Budget Position", "Structural Budget Position"
>>    ), var2 = c("United States", "United States", "United States",
>>    "Japan", "Japan", "Japan", "United States", "United States",
>>    "United States", "Japan", "Japan", "Japan"), value = c(NA,
>>    34.288, 31.831, 29.636, 30.539, 29.093, NA, 0, -2.7, -7.4,
>>    -5.7, -7)), .Names = c("Date", "variable", "var2", "value"
>> ), row.names = c(21L, 22L, 23L, 169L, 170L, 171L, 206L, 207L,
>> 208L, 354L, 355L, 356L), class = "data.frame")
>>
>> gp <- ggplot(g, aes(Date, value))
>> gp<- gp + geom_line()
>> gp <-gp + facet_grid(var2 ~ variable)
>> gp
>>
>> this works, but trying to get a bar chart version
>>
>> gp <- ggplot(g, aes(Date, value))
>> gp<- gp + geom_bar(stat="identity")
>> gp <-gp + facet_grid(var2 ~ variable)
>> gp
>>
>> gives the error
>> Error in if (!is.null(data$ymin) && !all(data$ymin == 0))
>> warning("Stacking not well defined when ymin != 0",  :
>>  missing value where TRUE/FALSE needed
>>
>> Is there something I can do to have a gap for missing data, as happens
>> with the line version?
>>
>> More generally, I may also have missing data between present data: e.g.
>>
>> is.na(g[5,4])<-TRUE
>>
>> and I would like if possible to simply see gaps at these points.
>>
>> Thanks for any help.
>>
>> Aidan
>>
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>