[R] dotchart for matrix data

[e-letter]

On 18/12/2010, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Dec 18, 2010, at 7:01 AM, e-letter wrote:
>
>> Readers,
>>
>> I am trying to use the function dotchart. The data is:
>>
>>> testdot
>>  category values1 values2 values3 values4
>> 1        a      10      27      56     709
>> 2        b       4      46      47     208
>> 3        c       5      17      18     109
>> 4        d       6      50      49     308
>>
>> The following error occurs
>>
>>> dotchart(testdot,groups=testdot[,2])
>> Error in dotchart(testdot, labels = testdot[, 1], groups = testdot[,
>> 2]) :
>>        'x' must be a numeric vector or matrix
>>
>> According to my understanding (clearly wrong!) of the documentation
>> for dotchart (accessed from the manual in section 'graphics'), columns
>> of data can be selected by 'groups' for subsequent plotting.
>
> The misunderstanding is in how you see the grouping information versus
> how R expects it. R generally expects such data in what is called
> "long" format, i.e. there will be one values columns and a category
> column. There are various ways to change the arrangement of your data.
> The function stack(), the function reshape(), or probably most
> commonly the function melt from reshape2 being the typical chosen
> routes.
>

Reshape and melt are not installed (version251) so for this task
manual rearrangement data is easier.

> require(reshape)
Loading required package: reshape
[1] FALSE
Warning message:
there is no package called 'reshape' in: library(package, lib.loc =
lib.loc, character.only = TRUE, logical = TRUE,
> library(reshape)
Error in library(reshape) : there is no package called 'reshape'
> mdot<-melt(dot)
Error: could not find function "melt"

However before doing so why this is relevant because of the
alternative creation objects 'testdot1'. Aren't these objects
suitable, since a (undesireable) graph was produced?

>> The
>> objective is to be able to create a dot chart where each row is
>> labelled according to the row names in the 'category' column and two
>> columns can be selected, e.g. 'values1' and 'values2'. Then I tried:
>>
>>> testdot1<-testdot[,1]
>>> testdot2<-testdot[,2]
>>> testdot3<-testdot[,3]
>>> dotchart(c(testdot2,testdot3),labels=testdot1)
>
> See if this is more to your liking:
>
> require(reshape)   # I'm not sure why I have reshape_0.8.3 rather than
> reshape2 loaded
>                     # I'm pretty sure Hadley would prefer that people
> use pkg:reshape2
>   mdot <- melt(dot)
> dotchart(mdot$value, groups=mdot$category, labels=mdot$variable)
> # OR more readable
> with(mdot, dotchart(value, groups=category, labels=variable)  )
>
> I'm not sure I got the roles of "values" and "category" correct, but
> it should be a simple matter to switch them in the dotcghart call if
> that is your pleasuRe.
>

I don't have dotcghart either.