Performs linear regression on one variable of the dataset.
linregression_onevar(dataset, x.val, metadata.vars, combination)
list representing the dataset from a metabolomics experiment.
the x-value to be tested.
metadata variables to use in linear regression. For example, c('variable1','variable2').
a formula specifying the model. For example, 'variable1+variable2'.
Returns a summary of the result from the lm function from stats package.