Variable names:

If variables have names not following R standard, some problem may still appear.

Solution:

Use variable names without space, parentheses or brackets, etc.

Error: Can only apply contrasts to data with 2 or more levels

This is an error that usually comes from attempting to fit a logistic model in R to data which does not have at least two different responses for each grouping variable.

For example, in data coded [0, 1] for incorrect and correct responses and two groups [m, f], it might be the case that no f in your data set responded inorrectly, meaning there are no f in the data with response 0. This will break the glm() function.

Ensure that there are no rows/columns in your data with no responses, and that there are no groups who only respond in a single way.

If this doesn’t seem to be the case for you, you may have encountered a bug: please feel free to contact me using a method at the bottom of this page.

Test ROC

The error messages in the Test ROC module are somewhat underdeveloped. If your answer is not here, please contact the author using the contact information at the end of this page.