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lessR (version 3.2)

Density: Density Curves from Data plus Histogram

Description

Abbreviation: dn

Plots a normal density curve and/or a general density curve superimposed over a histogram, all estimated from the data. Also reports the Shapiro-Wilk normality test and summary statistics.

If the provided object to analyze is a set of multiple variables, including an entire data frame, then each non-numeric variable in the data frame is analyzed and the results written to a pdf file in the current working directory. The name of each output pdf file that contains a bar chart and its path are specified in the output.

Usage

Density(x, data=mydata, n.cat=getOption("n.cat"), 

bw="nrd0", type=c("both", "general", "normal"), bin.start=NULL, bin.width=NULL,

col.fill=getOption("col.fill.pt"), col.bg=getOption("col.bg"), col.grid=getOption("col.grid"),

col.nrm="black", col.gen="black", col.fill.nrm=NULL, col.fill.gen=NULL,

cex.axis=.85, col.axis="gray30", x.pt=NULL, xlab=NULL, main=NULL, y.axis=FALSE, x.min=NULL, x.max=NULL, band=FALSE,

quiet=getOption("quiet"), pdf.file=NULL, pdf.width=5, pdf.height=5, ...)

dn(...)

Arguments

x
Variable(s) to analyze. Can be a single numerical variable, either within a data frame or as a vector in the user's workspace, or multiple variables in a data frame such as designated with the c
data
Optional data frame that contains the variable(s) of interest, default is mydata.
n.cat
For the analysis of multiple variables, such as a data frame, specifies the largest number of unique values of variable of a numeric data type for which the variable will be analyzed as a categorical. Set to 0 to turn off.
bw
Bandwidth of kernel estimation.
type
Type of density curve plotted. By default, both the general density and the normal density are plotted.
bin.start
Optional specified starting value of the bins.
bin.width
Optional specified bin width, which can be specified with or without a bin.start value.
col.fill
Default (for default color theme of "dodgerblue") is to display the histogram in a light gray. To suppress, the histogram, specify a color of "transparent".
col.bg
Color of the plot background.
col.grid
Color of the grid lines.
col.nrm
Color of the normal curve.
col.gen
Color of the general density curve.
col.fill.nrm
Fill color for the estimated normal curve, with a partially transparent blue as the default for a blue color theme, and transparent for all other themes.
col.fill.gen
Fill color for the estimated general density curve, with a partially transparent light red as the default as the default for a blue color theme, and transparent for all other themes.
cex.axis
Scale magnification factor, which by default displays the axis values to be smaller than the axis labels.
col.axis
Color of the font used to label the axis values.
x.pt
Value of the point on the x-axis for which to draw a unit interval around illustrating the corresponding area under the general density curve. Only applies when requesting type=general.
xlab
Label for x-axis.
main
Title of graph.
y.axis
Specifies if the y-axis, the density axis, should be included.
x.min
Smallest value of the variable x plotted on the x-axis.
x.max
Largest value of the variable x plotted on the x-axis.
band
If TRUE, add a rug plot, a direct display of density in the form of a narrow band beneath the density curve
quiet
If set to TRUE, no text output. Can change system default with set function.
pdf.file
Name of the pdf file to which graphics are redirected. If there is no filetype of .pdf, the filetype is added to the name.
pdf.width
Width of the pdf file in inches.
pdf.height
Height of the pdf file in inches.
...
Other parameter values for graphics as defined processed by plot, including xlim, ylim, lwd and cex.lab, col.main, density

Details

OVERVIEW Results are based on the standard dnorm function and density R functions for estimating densities from data, as well as the hist function for calculating a histogram. Colors are provided by default and can also be specified.

The default histogram can be modified with the bin.start and bin.width options. Use the Histogram function in this package for more control over the parameters of the histogram.

The limits for the axes are automatically calculated so as to provide sufficient space for the density curves and histogram, and should generally not require user intervention. Also, the curves are centered over the plot window so that the resulting density curves are symmetric even if the underlying histogram is not. The estimated normal curve is based on the corresponding sample mean and standard deviation.

If x.pt is specified, then type is set to general and y.axis set to TRUE.

DATA The data may either be a vector from the global environment, the user's workspace, as illustrated in the examples below, or one or more variable's in a data frame, or a complete data frame. The default input data frame is mydata. Can specify the source data frame name with the data option. If multiple variables are specified, only the numerical variables in the list of variables are analyzed. The variables in the data frame are referenced directly by their names, that is, no need to invoke the standard R mechanisms of the mydata$name notation, the with function or the attach function. If the name of the vector in the global environment and of a variable in the input data frame are the same, the vector is analyzed.

COLOR THEME Individual colors in the plot can be manipulated with options such as col.bars for the color of the histogram bars. A color theme for all the colors can be chosen for a specific plot with the colors option with the lessR function set. The default color theme is blue, but a gray scale is available with "gray", and other themes are available as explained in set, such as "red" and "green". Use the option ghost=TRUE for a black background, no grid lines and partial transparency of plotted colors.

VARIABLE LABELS If variable labels exist, then the corresponding variable label is by default listed as the label for the horizontal axis and on the text output. For more information, see Read.

PDF OUTPUT Because of the customized graphic windowing system that maintains a unique graphic window for the Help function, the standard graphic output functions such as pdf do not work with the lessR graphics functions. Instead, to obtain pdf output, use the pdf.file option, perhaps with the optional pdf.width and pdf.height options. These files are written to the default working directory, which can be explicitly specified with the R setwd function.

ONLY VARIABLES ARE REFERENCED The referenced variable in a lessR function can only be a variable name (or list of variable names). This referenced variable must exist in either the referenced data frame, mydata by default, or in the user's workspace, more formally called the global environment. That is, expressions cannot be directly evaluated. For example:

> Density(rnorm(50)) # does NOT work}

Instead, do the following: > Y <- rnorm(50) # create vector Y in user workspace > Density(Y) # directly reference Y

Based on the standard R function density, invisibly returns an object of class "density". For details see density.

[object Object],[object Object]

dnorm, density, hist, plot, rgb, shapiro.test.

# create data frame, mydata, to mimic reading data with Read function # mydata contains both numeric and non-numeric data mydata <- data.frame(rnorm(50), rnorm(50), rnorm(50), rep(c("A","B"),25)) names(mydata) <- c("X","Y","Z","C")

# normal curve and general density curves superimposed over histogram # all defaults Density(Y)

# short name dn(Y)

# save the density plot to a pdf file Density(Y, pdf.file="MyDensityPlot.pdf")

# suppress the histogram, leaving only the density curves # specify x-axis label per the xlab option for the plot function Density(Y, col.fill="transparent", xlab="My Var")

# specify (non-transparent) colors for the curves, # to make transparent, need alpha option for the rgb function Density(Y, col.nrm="darkgreen", col.gen="plum")

# display only the general estimated density # so do not display the estimated normal curve # specify the bandwidth for the general density curve, # use the standard bw option for the density function Density(Y, type="general", bw=.6)

# display only the general estimated density and a corresponding # interval of unit width around x.pt Density(Y, type="general", x.pt=2)

# variable of interest is in a data frame which is not the default mydata # access the breaks variable in the R provided warpbreaks data set # although data not attached, access the variable directly by its name Density(breaks, data=warpbreaks)

# densities for all numeric variables in a data frame Density()

# densities for all specified numeric variables in a list of variables # e.g., use the combine or c function to specify a list of variables Density(c(X,Y))histogram density color