The two datasets "mushroom.training" and "mushroom.test" were created using the "Mushroom Database".
The original dataset had another attribute that had missing values and has been removed. 
The training dataset contains 7423 examples and the test dataset 701 examples.
The first attribute is the class of each example ("e" or "p") and the rest (21 attributes) 
are categorical (nominal) attributes.

Next, we have the description of the database taken from UCI Knowledge Discovery in Databases Archive.
http://kdd.ics.uci.edu/

====================================================================================================================


1. Title: Mushroom Database

2. Sources: 
    (a) Mushroom records drawn from The Audubon Society Field Guide to North
        American Mushrooms (1981). G. H. Lincoff (Pres.), New York: Alfred
        A. Knopf
    (b) Donor: Jeff Schlimmer (Jeffrey.Schlimmer@a.gp.cs.cmu.edu)
    (c) Date: 27 April 1987

3. Past Usage:
    1. Schlimmer,J.S. (1987). Concept Acquisition Through Representational
       Adjustment (Technical Report 87-19).  Doctoral disseration, Department
       of Information and Computer Science, University of California, Irvine.
       --- STAGGER: asymptoted to 95% classification accuracy after reviewing
           1000 instances.
    2. Iba,W., Wogulis,J., & Langley,P. (1988).  Trading off Simplicity
       and Coverage in Incremental Concept Learning. In Proceedings of 
       the 5th International Conference on Machine Learning, 73-79.
       Ann Arbor, Michigan: Morgan Kaufmann.  
       -- approximately the same results with their HILLARY algorithm    

4. Relevant Information:
    This data set includes descriptions of hypothetical samples
    corresponding to 23 species of gilled mushrooms in the Agaricus and
    Lepiota Family (pp. 500-525).  Each species is identified as
    definitely edible, definitely poisonous, or of unknown edibility and
    not recommended.  This latter class was combined with the poisonous
    one.  The Guide clearly states that there is no simple rule for
    determining the edibility of a mushroom; no rule like ``leaflets
    three, let it be'' for Poisonous Oak and Ivy.

5. Number of Instances: 8124

6. Number of Attributes: 22 (all nominally valued)

7. Attribute Information: (classes: edible=e, poisonous=p)
     1. cap-shape:                bell=b,conical=c,convex=x,flat=f,
                                  knobbed=k,sunken=s
     2. cap-surface:              fibrous=f,grooves=g,scaly=y,smooth=s
     3. cap-color:                brown=n,buff=b,cinnamon=c,gray=g,green=r,
                                  pink=p,purple=u,red=e,white=w,yellow=y
     4. bruises?:                 bruises=t,no=f
     5. odor:                     almond=a,anise=l,creosote=c,fishy=y,foul=f,
                                  musty=m,none=n,pungent=p,spicy=s
     6. gill-attachment:          attached=a,descending=d,free=f,notched=n
     7. gill-spacing:             close=c,crowded=w,distant=d
     8. gill-size:                broad=b,narrow=n
     9. gill-color:               black=k,brown=n,buff=b,chocolate=h,gray=g,
                                  green=r,orange=o,pink=p,purple=u,red=e,
                                  white=w,yellow=y
    10. stalk-shape:              enlarging=e,tapering=t   
    11. stalk-surface-above-ring: ibrous=f,scaly=y,silky=k,smooth=s
    12. stalk-surface-below-ring: ibrous=f,scaly=y,silky=k,smooth=s
    13. stalk-color-above-ring:   brown=n,buff=b,cinnamon=c,gray=g,orange=o,
                                  pink=p,red=e,white=w,yellow=y
    14. stalk-color-below-ring:   brown=n,buff=b,cinnamon=c,gray=g,orange=o,
                                  pink=p,red=e,white=w,yellow=y
    15. veil-type:                partial=p,universal=u
    16. veil-color:               brown=n,orange=o,white=w,yellow=y
    17. ring-number:              none=n,one=o,two=t
    18. ring-type:                cobwebby=c,evanescent=e,flaring=f,large=l,
                                  none=n,pendant=p,sheathing=s,zone=z
    19. spore-print-color:        black=k,brown=n,buff=b,chocolate=h,green=r,
                                  orange=o,purple=u,white=w,yellow=y
    20. population:               abundant=a,clustered=c,numerous=n,
                                  scattered=s,several=v,solitary=y
    21. habitat:                  grasses=g,leaves=l,meadows=m,paths=p,
                                  urban=u,waste=w,woods=d
    
    22. stalk-root:               bulbous=b,club=c,cup=u,equal=e,
                                  rhizomorphs=z,rooted=r,missing=?

8. Missing Attribute Values: 2480 of them (denoted by "?"), all for
   attribute #22 that has been removed.

9. Class Distribution for training set: 
    --    edible: 3851 (51.8%)
    -- poisonous: 3572 (48.2%)
    --     total: 7423 instances