R help - May 2011 - barplot groups of different size i.e. height is NOT a matrix

Hello,

I want to use the function barplot do display several group of bars.
A standard example is given at this link
http://onertipaday.blogspot.com/2007/05/make-many-barplot-into-one-plot.html

But in their example the 4 groups of bars are all composed of 8 bars.
I want to be able do display the same kind of graph but where the number 
of bars in each group are not the same. For example the first group of 
bars would have 2 bars and the second group of bars would have 10 bars.

barplot function has a first parameter named height which is a matrix 
where each line  are the values  for the bars of one particular group.
One solution could be to have a height matrix with NA values but then 
the space occupied by each group is equal to the size of the largest 
group!! So you end up with gaps (empty) where there are NAs.

Do you know how to solve this problem?
Do i have to consider multiple barplots in the same plot with the same 
axis? (btw, i don't know how to do that)

In fact the bar would represent the performance of an algorithm.
A group of bars would be the performance of an algorithms with different 
parameters.
But when comparing different algorithms it is possible that we don't 
want to display the same number of parameters for each algorithm.

Thanks for your help.
Victor

Dear Victor,

Here is a basic solutions using ggplot2

library(ggplot2)
dataset <- data.frame(Main = c("A", "A", "A",
"B", "B"), Detail = c("a", "b",
"c", "1", "2"), value = runif(5, min = 0.5, max =
1))
ggplot(dataset, aes(x = Detail, y = value)) + geom_bar() + facet_grid(.~Main,
scales = "free_x")

Best regards,

Thierry
> -----Oorspronkelijk bericht-----
> Van: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
> Namens Victor Gabillon
> Verzonden: woensdag 25 mei 2011 14:56
> Aan: r-help at r-project.org
> Onderwerp: [R] barplot groups of different size i.e. height is NOT a matrix
> 
> Hello,
> 
> I want to use the function barplot do display several group of bars.
> A standard example is given at this link
> http://onertipaday.blogspot.com/2007/05/make-many-barplot-into-one-
> plot.html
> 
> But in their example the 4 groups of bars are all composed of 8 bars.
> I want to be able do display the same kind of graph but where the number of
> bars in each group are not the same. For example the first group of bars
would
> have 2 bars and the second group of bars would have 10 bars.
> 
> barplot function has a first parameter named height which is a matrix where
> each line  are the values  for the bars of one particular group.
> One solution could be to have a height matrix with NA values but then the
space
> occupied by each group is equal to the size of the largest group!! So you
end up
> with gaps (empty) where there are NAs.
> 
> Do you know how to solve this problem?
> Do i have to consider multiple barplots in the same plot with the same
axis?
> (btw, i don't know how to do that)
> 
> In fact the bar would represent the performance of an algorithm.
> A group of bars would be the performance of an algorithms with different
> parameters.
> But when comparing different algorithms it is possible that we don't
want to
> display the same number of parameters for each algorithm.
> 
> Thanks for your help.
> Victor
> 
> ______________________________________________
> 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.

On May 25, 2011, at 7:56 AM, Victor Gabillon wrote:
> Hello,
> 
> I want to use the function barplot do display several group of bars.
> A standard example is given at this link
>
http://onertipaday.blogspot.com/2007/05/make-many-barplot-into-one-plot.html
> 
> But in their example the 4 groups of bars are all composed of 8 bars.
> I want to be able do display the same kind of graph but where the number of
bars in each group are not the same. For example the first group of bars would
have 2 bars and the second group of bars would have 10 bars.
> 
> barplot function has a first parameter named height which is a matrix where
each line  are the values  for the bars of one particular group.
> One solution could be to have a height matrix with NA values but then the
space occupied by each group is equal to the size of the largest group!! So you
end up with gaps (empty) where there are NAs.
> 
> Do you know how to solve this problem?
> Do i have to consider multiple barplots in the same plot with the same
axis? (btw, i don't know how to do that)
> 
> In fact the bar would represent the performance of an algorithm.
> A group of bars would be the performance of an algorithms with different
parameters.
> But when comparing different algorithms it is possible that we don't
want to display the same number of parameters for each algorithm.
> 
> Thanks for your help.
> Victor

barplot() is fundamentally built upon the use of rect() to construct the bars,
so you could always create your own variant to allow for the flexibility that
you desire.

That being said, if your performance measures (the bar heights) are other than
discrete counts or proportions, I would advise you to consider using other
visual presentation forms, as these are really the only two types of data for
which barplots are generally considered satisfactory. A key to barplots of
course is that they are based at 0 for proper visual comparison. Thus, if you
need to have the minima of the relevant axis at a value other than 0, this is
another reason to not use them.

Even then, many folks have moved away from barplots to use point or dot plots
and similar formats, especially where you also need to include some type of
confidence interval for each measure.

HTH,

Marc Schwartz