Property	Value
Hex Value	`$05`
Categories	Catalog > B Stat Plot > Type
Localizations	FR: `Carré`

`Boxplot`

Overview

Defines Plot# (1, 2, or 3) of type

Availability: Token only available from within the Basic editor.

Syntax

Boxplot Plot#(type,Xlist[,freqlist,color#])

Arguments

Name	Type	Optional
type
Xlist	list
freqlist	list	Yes
color#	colorNum	Yes

Location

2nd, stat plot

Description

The commands Plot1(, Plot2(, and Plot3(, which are identical except for which stat plot (1, 2, or 3) they affect, define their corresponding stat plot. When the stat plot is defined, it is also turned on so no PlotsOn command is necessary.

The first argument of the commands is always the type of plot, and is one of Scatter, xyLine, Histogram, Boxplot, ModBoxplot, and NormProbPlot - these types are found in the TYPE submenu of the stat plot menu. The other arguments vary. For all but Histogram and Boxplot, there is a mark argument - this is a dot, a cross, or a box, symbols that can be found in the MARK submenu of the stat plot menu. On color calculators, there is an optional final argument to specify the color of the plot.

Scatter plot

Plot#(Scatter, x-list, y-list, mark) defines a scatter plot. The points defined by x-list and y-list are plotted using mark on the graph screen.

x-list and y-list must be the same length.

xyLine plot

Plot#(xyLine, x-list, y-list, mark) defines an xyLine plot. Similarly to a scatter plot, the points defined by x-list and y-list are plotted using mark on the graph screen, but with an xyLine plot they are also connected by a line, in the order that they occur in the lists.

x-list and y-list must be the same length.

Histogram plot

Plot#(Histogram, x-list, freq list) defines a Histogram plot. The x-axis is divided into intervals that are Xscl wide. A bar is drawn in in each interval whose height corresponds to the number of points in the interval. Points that are not between Xmin and Xmax are not tallied.

Xscl must not be too small - it can divide the screen into no more than 47 different bars.

Box plot

Plot#(Boxplot, x-list, freq list) defines a box plot. A rectangular box is drawn whose left edge is Q₁ (the first quartile) of the data, and whose right edge is Q₃ (the third quartile). A vertical segment is drawn within the box at the median, and 'whiskers' are drawn from the box to the minimum and maximum data points.

The box plot ignores the Ymax and Ymin dimensions of the screen, and any plots that aren't box plots or modified box plots. Each box plot takes approximately 1/3 of the screen in height, and if more than one are plotted, they will take up different areas of the screen.

Modified box plot

Plot#(ModBoxplot, x-list, freq list, mark) defines a modified box plot. This is almost entirely like the normal box plot, except that it also draws outliers. Whiskers are only drawn to the furthers point within 1.5 times the interquartile range (Q₃-Q₁) of the box. Beyond this point, data points are drawn individually, using mark.

The box plot ignores the Ymax and Ymin dimensions of the screen, and any plots that aren't box plots or modified box plots. Each box plot takes approximately 1/3 of the screen in height, and if more than one are plotted, they will take up different areas of the screen.

Normal probability plot

Plot#(NormProbPlot, data list, data axis, mark) defines a normal probability plot. The mean and standard deviation of the data are calculated. Then for each point, the number of standard deviations it is from the mean is calculated, and the point is plotted against this number using mark. data axis can be either X or Y: it determines whether the value of a point determines it's x-coordinate or y-coordinate.

The point behind this rather convoluted process is to test the extent to which the data is normally distributed. If it follows the normal distribution closely, then the result will be close to a straight line - otherwise it will be curved.

Advanced Uses

After doing a regression, a scatter plot of ʟRESID against the x-list is a useful measure of the effectiveness of the regression. If the plot appears random, this is a good sign; if there is a pattern to the plot, this means it's likely that a better regression model exists.

Optimization

The ʟ symbol at the beginning of list names can be omitted everywhere in this command.

In addition, every element except the plot type and the data list or data lists are optional, and take on the following default values:

freq list is 1 by default, meaning that all frequencies are 1.
mark is the box by default.
data axis is X by default.

Error Conditions

ERR:DIM MISMATCH is thrown if the x and y lists, or the data and frequency lists, have different dimensions.
ERR:STAT is thrown if Xscl is too small in the case of a Histogram.

All errors are thrown when plotting the stat plot, as opposed to when the command is executed, and do not provide a 2:Goto option.

Source: parts of this page were written by the following TI|BD contributors: DarkerLine, GoVegan, Myles_Zadok.

History

Calculator	OS Version	Description
TI-82	1.0	Added

Authors: Adrien Bertrand

Boxplot