comment #41 :
If is.null(variables) the slot pramVars is checked, if it is.null too =>
ERROR, else variables in the slot used.

If !is.null(variables) only this information is used.

If pram is applied several times on the same variable, should it use the
original data as input each time or the output from the previous pram
run??? At the moment it uses the previous pram run output.
Merge branch 'master' of https://github.com/alexkowa/sdcMicro.git