Improve spending function summary display

[nanxstats]

When using sfLDOF(), the summary text can be a bit confusing:

summary(sfLDOF(alpha = 0.25, t = 0.5, param = 0))
#> "Lan-DeMets O'Brien-Fleming approximation spending function with none = 1"

@elong0527 wonders if it makes more sense to display "... with no parameters".

Since the relevant logic in sfLDOF() seems intentional and might be written this way for a reason, I will let you make the decision.

Technical details

The call sequence is summary.spendfn() -> sfLDOF(). Here, since param = 0, sfLDOF() will set param to 1, and set parname to "none". Then summary.spendfn() will print parname = param (none = 1).

gsDesign/R/gsMethods.R

Lines 811 to 816 in cbf9a94

	} else {
	s <- paste(object$name, "spending function")
	if (!is.null(object$parname) && !is.null(object$param)) {
	s <- paste(s, "with", paste(object$parname, collapse = " "), "=", paste(object$param, collapse = " "))
	}
	}

gsDesign/R/gsSpending.R

Lines 711 to 717 in cbf9a94

	if (is.null(param) || param < .005 || param > 20) param <- 1
	checkScalar(param, "numeric", c(.005,20),c(TRUE,TRUE))
	t[t>1] <- 1
	if (param == 1){
	rho <- 1
	txt <- "Lan-DeMets O'Brien-Fleming approximation"
	parname <- "none"

[nanxstats]

@elong0527 do you want to take a quick look at this?