Teaching:TUW - UE InfoVis WS 2007/08 - Gruppe 07 - Aufgabe 1 - Histogram: Difference between revisions

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= Example =
= Example =
As an example we consider values given from the table below to create a histogram (right image). The data derived from the first column of the table shows the class affiliation. According to the table values these classes are aligned along the x-axis of the histogram. Frequenzy values according to the classes are then printed along the y-axis of the histogram. Once this is properly done, the histogram shows the amount of members according to any of the classes.  
As an example we consider values given from the table below to create a histogram (right image). The data derived from the first column of the table shows the class affiliation. According to the table values these classes are aligned along the x-axis of the histogram. Frequenzy values according to the classes are then printed along the y-axis of the histogram. Once this is properly done, the histogram shows the amount of frequency according to any of the classes. Hence the histogram is a powerful visualisation that can make information accessable in just a few seconds, considering that the table on the left side is representing the same information, it is easy to understand the power of graphical visualisation.


<table style="height:16px" border="0">
<table style="height:16px" border="0">

Revision as of 14:06, 7 November 2007

Definitions

In statistics, a histogram is a graphical display of tabulated frequencies. A histogram is the graphical version of a table that shows what proportion of cases fall into each of several or many specified categories. The histogram differs from a bar chart in that it is the area of the bar that denotes the value, not the height, a crucial distinction when the categories are not of uniform width (Lancaster, 1974). The categories are usually specified as non-overlapping intervals of some variable. The categories (bars) must be adjacent.
[Wikipedia, 2007]


Read full article on Wikipedia
A histogram is used when we want to show frequencies of a continous variable. The continous variable can, of course, assume all values within an interval and the histogram reflects this by covering the whole of the interval concerned.
[Wallgreen et al., 1996]


Explanation

TODO PETER ... WEBSTERs ...

Example

As an example we consider values given from the table below to create a histogram (right image). The data derived from the first column of the table shows the class affiliation. According to the table values these classes are aligned along the x-axis of the histogram. Frequenzy values according to the classes are then printed along the y-axis of the histogram. Once this is properly done, the histogram shows the amount of frequency according to any of the classes. Hence the histogram is a powerful visualisation that can make information accessable in just a few seconds, considering that the table on the left side is representing the same information, it is easy to understand the power of graphical visualisation.

Frequency Table

class j absolute frequency nj class interval w j
1 (=> 24 ≤ x ≤ 26 ) 36 3
2 (=> 26 < x ≤ 28 ) 37 2
3 (=> 28 < x ≤ 33 ) 17 5
Histogram Illustration

Frequency density (height of a column) = n j / w j

Related Links

References

  • [Wikipedia, 2007] Wikipedia, Histogram. Retrieved at: November 01, 2007. http://en.wikipedia.org/wiki/Histogram
  • [Wallgreen et al., 1996] Anders Wallgreen, Britt Wallgreen, Rolf Persson, Ulf Jorner and Jan-Aage Haaland. Graphing Statistics & Data: Creating Better Charts. SAGE Publications, Thousand Oaks, London, New Delhi, 1996.
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