Performs linear regression analysis over the dataset with the selected metadata's variables.
linreg_all_vars(dataset, metadata.vars, combination)
list representing the dataset from a metabolomics experiment.
metadata variables to use in linear regression. For example, c('variable1','variable2').
a formula specifying the model. For example, 'variable1+variable2'.
Returns a list where each element is the linear regression result of a variable on the dataset.