draw.cum draws a cumulative distribution function.  It is still under development (6/18/2013).

ARGUMENTS

cumFn = a cumulative distribution function.  
Example:  cumFn = function(x) pgamma( x, shape = 1.0, rate = 1.0 )

x.range defaults to c( -10^6, 10^6 ).  If xlim is NULL, then draw.cum finds values xLower and xUpper such that x.range[1] < xLower < xUpper < x.range[2] such that such that cumFn( xLower ) = y.range[1] and cumFn( xUpper ) = y.range[2].  If xlim is non-null, then xLower = xlim[1] and xUpper = xlim[2].  

y.range defaults to c( 0.001, 0.999 ).  

xlim defaults to NULL. If xlim is NULL, then xlim will be set to values such that cumFn( xlim[1] ) = y.range[1] and cumFn( xlim[2] ) = y.range[2].  If xlim is non-NULL, then y.range has no effect, and cumFn will be plotted in the range from xlim[1] to xlim[2].  

ylim defaults to c( 0, 1 ).  

lwdMain controls the line width - it defaults to 2.  

nGrid controls the number of equally spaced values at which cumFn is computed between xlim[1] and xlim[2].  It defaults to 10^3.

'draw.f' draws an F distribution with the specified df's.
Optionally it draws in the F observed and the area corresponding
to the  p-value.
ARGUMENTS:
'df1', 'df2' are the degrees of freedom for the numerator and
denominator, respectively.
Fobs is the observed value of the F.  This is an optional parameter.
If it is used, the function plots the area corresponding to the pvalue
as well as the F distribution.
'Xmax' is an optional paramter.  Use it to control the maximum value
on the X-axis.
'Ymax' is an optional paramter.  Use it to control the maximum value
on the Y-axis.  Ymax is especially useful for F(1, df2) and F(2, df2)
because these distributions get extremely large close to zero.

'draw.inv.gamma' computes the X-Y coordinates for an inverse gamma probability density or cumulative distribution function.  It either plots the function or simply outputs the coordinates.  

ARGUMENTS: 

'shape' = shape parameter

'rate' = rate parameter.  Note that you only need to specify the 'rate' or the 'scale' but not both.  If both are specified, then the 'scale' parameter takes precedence.

'scale' = scale parameter.  See comment about the 'rate' parameter.

'xlimit=NA' permits user control of the x axis limits.

'ylimit=NA' permits user control of the y axis limits.

'plot.dist = TRUE' (default).  If FALSE, then no plot is made and the X-Y coordinates for the graph are outputted.  If TRUE, a plot is made and the coordinates are not outputted.

Label = "default":  The default setting creates a graph title that states the parameters of the gamma distribution.  The label can be set to other values if preferred.

'lwd' controls the line weight on the graph.

'cred.int' & 'plot.cred.int' control whether or not a credible interval is plotted and the probability level of the credible interval.  At present, only a two-sided credible interval is implemented, but in the future, I would like to offer the option of plotting the credible interval in the left or right tail of the distribution.  

'cred.lab' controls whether or not the probability level of the credible interval is plotted inside of the density plot.

'cred.col' controls the color of the area under the credible interval.