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# Scatter Plots - Conceptual Design
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_Graßnick_
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This document describes the conceptual ideas behind the implementation of the [ScatterplotRasterizer](https://gitlab.hrz.tu-chemnitz.de/s9444737--tu-dresden.de/brailleplot/blob/master/src/main/java/de/tudresden/inf/mci/brailleplot/rendering/ScatterPlotRasterizer.java).
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## Layout
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![scatterplot_layout](img/ScatterPlot_layout.svg)
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Following the guidelines for tactile diagrams by Engel [1], the following aspects have been taken into account for the creation of the layout.
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First of all, only requirement elements are created. This includes the title, the axis with their tick marks and their according labels, as well as the axis descriptions. There are no decorations.
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The title is placed in the upper left corner so that that is the first object, the reader gets in contact with. This way, the purpose of the document is clear right from the start.
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Following the title, there is a vertical gap with the height of one Braille cell. This is supposed to help the reader distinguish between the title and the following content, which must not be interpreted as Braille text.
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The origins of both the x axis and the y axis are always located in the lower left corner. Again, this ensures the reader can easily find the origin of the axis in consecutive documents.
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As remarked in the presentation of the project, the origin could be placed in the upper left corner, right beneath the title in order to support the reading flow.
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This idea is a possible issue for further user studies.
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Because of the standardized size of Braille cells and thus the limited resolution of generic Braille text embossers, space is very valuable. I thus decided to move the description of the axis to the legend, rather than printing them next to the axis. In the first brief tests with two visually impaired test candidates, there where no issues concerning the comprehensibility.
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In order to separate the axis from the actual plotted data points, a gap of one Braille cell is introduced. Otherwise, data points which where rendered directly onto the axis could not be recognized anymore.
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The remaining space is used for the actual data representation.
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## Example Plot
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![scatterplot_example](img/ScatterPlot_example.svg)
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![scatterplot_example_legend](img/ScatterPlot_example_legend.svg)
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## References
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[1] Engel, C: Kriterien zur Erstellung taktiler Diagramme und Diagrammbeschreibungen. Technische Universität Dresden, Professur Mensch-Computer Interaktion. |
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