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 (second column) 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. | 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 (second column) 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. | ||
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<tr> | <tr> | ||
<td>1 (=> 24 ≤ x ≤ 26 )</td> | <td>1 (=> 24 ≤ x ≤ 26 )</td> | ||
<td | <td>36</td> | ||
<td | <td>3</td> | ||
</tr> | </tr> | ||
<tr> | <tr> | ||
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<td>5</td> | <td>5</td> | ||
</tr> | </tr> | ||
<b>Frequency density</b> (height of a column) = n <sub> j </sub> / w <sub> j </sub></ br> | <b>Frequency density</b> (height of a column) = n <sub> j </sub> / w <sub> j </sub> </br> | ||
<b>Frequency (area)</b> = Width x Height | <b>Frequency (area)</b> = Width x Height | ||
</table></td> | </table></td> |
Revision as of 11:01, 8 November 2007
Definitions
Explanation
A histogram is a representation of a frequency distribution by using rectangles. The width of the rectangle (x axis) represents different values included into one class whereas the height specifies the number of elements that belong into this class (divided by the number of different values in each class). The size of an area of each column (not its height) specifies how many data-elements of each class occur in the total data set. Histograms are widely being used in statistics but we can also find them in practical appliances in our everyday life as well, e.g. digital cameras.
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 (second column) 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 density (height of a column) = n j / w j Frequency (area) = Width x Height
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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.