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classification tables

3 messages · Taka Matzmoto, Philippe GROSJEAN, Gabor Grothendieck

Original
Taka Matzmoto
# 
Dear R-users

I have two vectors. One vector includes true values and the other vector has 
estimated values. Values are all integers from 1 to 4.

For example,

x <- c(1,2,3,4,2,3,3,1,2,3)
y <- c(2,1,3,4,1,3,3,2,2,3)

I would like to a classfication table x by y. With the table, I would like 
to calculate what percentage is correct classfication.

Which R function do I need to use for creating a 4 * 4 classification table?

Thank you.

Taka,
Philippe GROSJEAN
# 
> y <- c(2,1,3,4,1,3,3,2,2,3)
 > table(x, y)
    y
x   1 2 3 4
   1 0 2 0 0
   2 2 1 0 0
   3 0 0 4 0
   4 0 0 0 1
 > ?table

Best,

Philippe Grosjean

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( ( ( ( (    Prof. Philippe Grosjean
  ) ) ) ) )
( ( ( ( (    Numerical Ecology of Aquatic Systems
  ) ) ) ) )   Mons-Hainaut University, Belgium
( ( ( ( (
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Taka Matzmoto wrote:
Gabor Grothendieck
# 
Also check out CrossTable in the gmodels package.

Regarding your other question, assuming we have
tab<-table(x,y) as in Philippe's post, the fraction of
pairs in x and y that match can be calculated via
any of these:

  sum(x==y) / length(x)

  sum(diag(tab)) / sum(tab)

  library(e1071)
  classAgreement(tab) # tab from above

  sum(diag(prop.table(tab)))
On 8/7/06, Philippe Grosjean <phgrosjean at sciviews.org> wrote: