Update plotgsPower() to use offset arg for Future Analysis legend

[jdblischak]

I changed the legend title from Analysis to Future Analysis. I did this by directly updating the column name in the underlying data that is passed to {ggplot2}. An alternative would be to keep the column name as Analysis and only change the legend title. Please let me know if that would be preferred.

I also added an argument offset to add an arbitrary integer value to the Future Analysis legend labels. I added a roxygen2 @param for this argument, but it's not being used. AFAICT there is no man page for plotgsPower(), but I am not familiar with {sinew}

Demonstration

library("gsDesign")
x <- gsDesign(test.type = 1, delta1 = 0.3, sfu = sfLDOF)

# Future Analysis: 1, 2, 3
gsDesign:::plotgsPower(x)

# Future Analysis: 2, 3, 4
gsDesign:::plotgsPower(x, offset = 1)

[jdblischak]

cc @keaven @nanxstats

[jdblischak]

Here is how to recreate the above plots without directly accessing the internal function via ::::

library("gsDesign")
x <- gsDesign(test.type = 1, delta1 = 0.3, sfu = sfLDOF)

# Future Analysis: 1, 2, 3
plot(x, plottype = 2)

# Future Analysis: 2, 3, 4
plot(x, plottype = 2, offset = 1)

[jdblischak]

I've enabled the following behavior for the legend title:

• Default to "Analysis"
• If offset > 0, default to "Future Analysis"
• Either of the above defaults can be overridden by passing the argument titleAnalysisCustom (Note: I can change the formatting of this variable name. I couldn't figure out the style from the file. Most of the variable names are single words, so I didn't know how to name a multi-word variable. I went with camelCase, but I can switch to whatever)

Here is some example code to demonstrate the latest behavior:

library("gsDesign")
x <- gsDesign(test.type = 1, delta1 = 0.3, sfu = sfLDOF)

# Analysis: 1, 2, 3
plot(x, plottype = 2)

# Future Analysis: 2, 3, 4
plot(x, plottype = 2, offset = 1)

# Custom label: 2, 3, 4
plot(x, plottype = 2, offset = 1, titleAnalysisCustom = "A custom label")