setBetaspendfString: Function that sets the expression of the base beta spending function as a string
Description
Sets the expression of the base beta spending function as a string.
This function is only used if one needs to display the base beta spending function as a string. This function DOES NOT update the base beta spending function. One can use setBaseBetaspendf() to change the base beta spending function. The spending functions and their string expressions should be defined only once per object. They should not be updated during any interim update to the design.
Usage
setBetaspendfString(theObject, string0)
Value
an object of class "sequential.design"
Arguments
theObject
The sequential design object
string0
The string of the expression of the base beta spending function. Its argument need to be 't'.