Minimal gain value

MonikaBeee

Hi guys,
Someone could please help me in my homework? 
I need to use a csv file to make a process based on a decision tree model. Then the question is: what is the largest minimal gain value where  the C4.5 tree has not got only one leaf?
Thanks in advance!
Monika

BalazsBaranyRM

Hi @MonikaBeee,

you could import your CSV file into the repository, or use Read CSV to read the data on the file in the process.
You should mark the label attribute using Set Role.
Then you let a Decision Tree build a model from your data.

For determining the minimal gain you could manually iterate (e. g. start from 0.4 and go down, or from 0.001 and go up), first in larger, then in smaller steps and look at the resulting until you find the threshold you're searching for. However, other parameter settings could also influence the result. 

A more elegant way is using a loop to automatically try different parameter values and determining the tree complexity. For example there is Decision Tree to ExampleSet in the Converters extension that you could use to find the number of rules in the tree and then filter the appropriate lines. 

Regards,
Balázs