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nan_boxplot

Draw a box-and-whiskers plot for data provided as column vectors.

Calling Sequence

nan_boxplot(y1[,y2,...])
nan_boxplot(y1[,y2,...],G)
nan_boxplot(Y_list)

Parameters

y1,y2,... :

vectors and/or matrixes with data as column vectors (of varying length)

G:

string vector defines the column by strings

Y_list :

list of vectors and/or matrixes with data as column vectors (of varying length)

Description

A boxplot (also known as a box-and-whisker plot is a way of graphically depicting groups of numerical data through their five-number summaries (the smallest observation, lower quartile (Q1), median, upper quartile (Q3), and largest observation). A boxplot may also indicate which observations, if any, might be considered outliers. The boxplot was invented in 1977 by the American statistician John Tukey.

For each data series a box is drawn to indicate the position of the lower and upper quartile of the data. The box has a centre line indicating the median of the data. Straigh center lines (the whiskers) above and below the box indicates the maximum and minimum values in the data set (except for outliers). Outliers are defined as any points larger than Q3 + 1.5*IQR or lower then Q1 - 1.5*IQR, where IQR is the inter quartile range defined as IQR=Q3-Q1. Outliers are plotted as individual '*'.

Boxplots can be useful to display differences between populations without making any assumptions of the underlying statistical distribution. The spacings between the different parts of the box help indicate the degree of dispersion (spread) and skewness in the data, and identify outliers.

Examples

nan_boxplot([rand(10,5);5*rand(5,5)-2.5])
nan_boxplot() // demo and help

Bibliography

http://en.wikipedia.org/wiki/Box_plot

Authors


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