partcov: partial covering

A convolution model to convert some absorption model into a partial covering absorption. If the absorption model is M(E) then this is converted to (1-CvrFract) + Cvrfact * M(E). Note that when specifying the model it is important to put parentheses in the right place. Let this model be P(E) which we want to apply to an absorption model M(E) then use the result to multiply an additive model A(E). The combined model should be specified as (P*M)*A, not P*M*A or P*(M*A).

The parameters are:

par1=CvrFract Covering fraction (0 <par1 <1).