getMinMax: Finds a Reasonable Domain for Plotting a Graph

Description

This function computes a reasonable domain for plotting one, two, or three distribution functions by truncating small tail probabilities. This function also lists the population medians.

Usage

getMinMax(xmin = NULL, xmax = NULL, distA, parmA1 = NULL, parmA2 = NULL, distB = NULL, 
          parmB1 = NULL, parmB2 = NULL, distC = NULL, parmC1 = NULL, parmC2 = NULL)

Arguments

xmin

A lower bound, usually set to NULL during input.

xmax

An upper bound, usually set to NULL during input.

distA

Character variable naming the first probability density function (starting with "d") or cumulative density function (starting with "p").

parmA1

The first argument in distA, excluding the dummy argument. Alternatively, parmA1 may be set to be a vector of arguments, excluding the dummy argument.

parmA2

The second argument in distA, excluding the dummy argument. Alternatively, parmA2 may be set to be a vector of arguments, excluding the dummy argument and parmA1.

distB

Character variable naming the second probability density function (starting with "d") or cumulative density function (starting with "p").

parmB1

The first argument in distB, excluding the dummy argument. Alternatively, parmB1 may be set to be a vector of arguments, excluding the dummy argument.

parmB2

The second argument in distB, excluding the dummy argument. Alternatively, parmB2 may be set to be a vector of arguments, excluding the dummy argument and parmB1.

distC

Character variable naming the third probability density function (starting with "d") or cumulative density function (starting with "p").

parmC1

The first argument in distC, excluding the dummy argument. Alternatively, parmC1 may be set to be a vector of arguments, excluding the dummy argument.

parmC2

The second argument in distC, excluding the dummy argument. Alternatively, parmC2 may be set to be a vector of arguments, excluding the dummy argument and parmC1.

Value

xmin

A reasonable value of a lower bound for the domain of a graph.

xmax

A reasonable value of an upper bound for the domain of a graph.

medianA

The population median of distA.

medianB

The population median of distB.

medianC

The population median of distC.

Details

This function getMinMax is automatically called by plotDist and shadeDist, so the user does not actually need to directly call getMinMax when executing plotDist and shadeDist. This function by itself does not construct a graph.

Examples

Run this code

# NOT RUN {
getMinMax(  , , "dnorm", 20, 5  ) # Normal(mu=20, sigma=5)

# Standard normal, and t with 4 degrees of freedom
getMinMax(  , , "dnorm", 0, 1, "dt", 4, 0 ) 

# Standard normal, central t with 4 d.f., and t with 4 d.f. and non-centrality parmater = 1.2
getMinMax(  , , "dnorm", 0, 1, "dt", 4, 0, "dt", 4, 1.2 ) 

# Force minimum to be -3.
getMinMax( -3, , "dnorm", 0, 1 )

# Force maximum to be 3.
getMinMax( , 3, "dnorm", 0, 1 )
# }