Add covariate expression to a function string

addCovariate(funstring, varName, covariate, theta, isLog)

## Arguments

funstring a string giving the expression that needs to be modified the variable to which the given string corresponds to in the model expression the covariate expression that needs to be added (at the appropriate place) a list of names of the 'theta' parameters in the 'fit' object a boolean signifying the presence of log-transformation in the funstring

## Value

returns the modified string with the covariate added to function string

## Author

Vipul Mann, Matthew Fidler