R help - Mar 2010 - Frequencies from a matrix - spider from frequencies

First of all, I really like R! Still being a newbie, I find things (the 
difficult ones) to be very simple.
Alas, some 'simple' things still escape me. (Maybe the tutorials are 
often too much focused on the 'difficult' items??)

Here comes my 'problem', over which I have sweated for the last 2 hours:
My data are of a matrix 10x31, Likert Scale (1-5). 10 questions, 31 
respondents. Now, I want to display the frequencies per question. I have 
not found any better (any more simple) than
for (in in 1.10) print (table(learn[,i]))
And then, still, the scale is printed 10 times as well. I am sure, there 
is a better function, but I didn't find one.
Actually, I would want the scale once, atop ('names'), and then the 
10(questions) * 5 (length.of.scale) thereunder, like
     1 2 3 4 5
1   3 4 2 1 2
2   5 9 2 1 4
3   4 4 6 1 3
....

And, now somewhat less of the ordinary, a spider/radar showing the 
number of responses for each question (circular axis, 10), with the 
frequencies as radial axes. That is, 5 polygons showing the frequencies 
of the responses per each question.

Any help is appreciated, and my excuses for asking a simple question,

Uwe

Hi:

The first part is straightforward. You didn't supply example data,
but it's easy to generate it oneself:

likmat <- matrix(sample(1:5, 310, replace = TRUE), nrow = 31)
dim(likmat)
# [1] 31 10
frq <- t(apply(likmat, 2, table))   # 10 x 5 matrix, questions in rows

As for the plot,
?stars

The stars() function allows one to generate spider/radar plots as you
requested. Since there are several forms that it can take, I suggest
you run the example:

example(stars)

and mimic the one(s) you want.

HTH,
Dennis

On Mon, Mar 15, 2010 at 12:24 AM, Uwe Dippel <udippel@uniten.edu.my>
wrote:
> First of all, I really like R! Still being a newbie, I find things (the
> difficult ones) to be very simple.
> Alas, some 'simple' things still escape me. (Maybe the tutorials
are often
> too much focused on the 'difficult' items??)
>
> Here comes my 'problem', over which I have sweated for the last 2
hours:
> My data are of a matrix 10x31, Likert Scale (1-5). 10 questions, 31
> respondents. Now, I want to display the frequencies per question. I have
not
> found any better (any more simple) than
> for (in in 1.10) print (table(learn[,i]))
> And then, still, the scale is printed 10 times as well. I am sure, there is
> a better function, but I didn't find one.
> Actually, I would want the scale once, atop ('names'), and then the
> 10(questions) * 5 (length.of.scale) thereunder, like
>    1 2 3 4 5
> 1   3 4 2 1 2
> 2   5 9 2 1 4
> 3   4 4 6 1 3
> ....
>
> And, now somewhat less of the ordinary, a spider/radar showing the number
> of responses for each question (circular axis, 10), with the frequencies as
> radial axes. That is, 5 polygons showing the frequencies of the responses
> per each question.
>
> Any help is appreciated, and my excuses for asking a simple question,
>
> Uwe
>
> ______________________________________________
> R-help@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.
>
	[[alternative HTML version deleted]]

Uwe Dippel-2 wrote:
> 
> Here comes my 'problem', over which I have sweated for the last 2
hours:
> My data are of a matrix 10x31, Likert Scale (1-5). 10 questions, 31 
> respondents. Now, I want to display the frequencies per question. I have 
> not found any better (any more simple) than
> for (in in 1.10) print (table(learn[,i]))
> 

Dennis has shown one way to do it. I personally prefer to arrange the data
in the "long" format shown below from the beginning, because it is
much more
flexible when I want to derive summaries and plot the data:


nsubj = 5
nquest= 4
d = matrix(as.integer(runif(nsubj*nquest,1,6)),nrow=nquest)
colnames(d) = paste("subj",1:nsubj,sep="")
rownames(d) = paste("quest",1:nquest,sep="")
# These data are in the wide format

# Convert data to the "long" format. It is much more flexible,
# for example when you have missing data, and is the format of choice
# when data are stored in a database. 
# 
dframe = data.frame(
  quest = rep(rownames(d),nsubj), 
  subj  = rep(colnames(d), nquest),
  resp  = as.vector(d)
  )
dframe
# Now we have the data in the long format, and the world is our limit
# Give it a first try with xtabs
xtabs(resp~quest+subj,data=dframe)
# oops, not that, that is the original
# Try ftable: looks good
ftable(resp~quest,data=dframe)

For the spider see ?star or 

http://addictedtor.free.fr/graphiques/RGraphGallery.php?graph=63

Dieter



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On 03/15/2010 06:24 PM, Uwe Dippel wrote:
> ...
> And, now somewhat less of the ordinary, a spider/radar showing the
> number of responses for each question (circular axis, 10), with the
> frequencies as radial axes. That is, 5 polygons showing the frequencies
> of the responses per each question.
>
Hi Uwe,
Here's one way to get your spider plot:

ld1<-matrix(sample(1:5,310,TRUE),nrow=31)
ld2<-apply(ld1,2,table)
radial.plot(ld2,line.col=2:6,rp.type="p",
  radial.pos=seq(0,9*pi/5,by=pi/5),
  labels=paste("Q",1:10,sep=""),start=pi/2,
  clockwise=TRUE,main="Frequency of response by question")
par(xpd=TRUE)
legend(8,12,1:5,col=2:6,lty=1)
par(xpd=FALSE)

Quite a bit of overlap on the polygons, however.

Jim