| additive | (adj. or v) A process or state whereby elements combine together, such as two primitive shapes combining to form a larger, more complex one. Additive is the opposite of subtractive.
(See 192)
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| bar graph | (n) A graph (usually 2-D) in which one dimension represents the independent variable and the other represents the dependent variable. The magnitude of the dependent variable is represented by a line or area of uniform width (a bar).
(See 207)
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| contour line | (n) A line that represents the independent variable (X,Y) combinations that result in a constant dependent variable value (also called an isoline). Acontour line can also represent the juncture between two surfaces of differing orientations or depths. In this definition, a contour line is an alternate term for edge.
(See 210)
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| contour plot | (n) A visualization in which the horizontal and vertical scales both represent independent variable values, and the contour lines show the mapping of constant, dependent variable values. Multiple contour lines are typically drawn on a plot, representing a uniform sampling of dependent variable values.
(See 210)
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| cutting plane | (n) An imaginary plane in space used to define the division between two parts of an object. Acutting plane is often used to define a portion of an object to be removed in order to reveal the interior detail.
(See 193)
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| data region | (n) The region in a visualization where the actual data is represented. In a graph or plot, the region would be bounded by the scales (axes) where the point or line markers representing the data are drawn.
(See 206)
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| dependent variable | (n) A variable dependent on the response of the model and not controlled by the experimenter. Every dependent variable value is paired with one or more independent variables and represents the model’s response to the independent variable values.
(See 206)
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| development | (n) An alternative description of the surfaces of a 3-D object as a 2-D pattern. The creation of a development is often thought of as an unfolding of the surfaces of an object. Adevelopable surface, then, can be unfolded or unrolled onto a plane without distortion. Single-curved surfaces, such as cylinders and cones, are also developable.
(See 197)
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| double-curved surface/line | (n) A surface or line that curves in two orthogonal dimensions at the same time. A sphere is an example of a double-curved surface.
(See 198)
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| edge | (n) The intersection or boundary of two nontangential surfaces (faces). An edge is represented on a technical drawing as a line or a change in shading gradients in a rendered image.
(See 190)
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| face | (n) A distinct planar or curved surface or region on an object. One or more faces joined together at edges define the boundary between object and nonobject. A face is a topological element in a 3-D model.
(See 190)
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| glyph | (n) A compound mark used in a visualization that cannot be classified by other commonly used marks. Glyphs are usually custom designed to encode multiple elements of data into a single mark. The objective for designing glyphs or any other marks is to tap into the innate perceptual abilities of the viewer.
(See 204)
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| image plane | (n) An imaginary plane on which an object is projected. The graphic representation of an object on a computer screen or paper is an example of a projection as it would appear on an image plane.
(See 199)
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| inclined face | (n) A planar face (surface) of an object that has been rotated about one axis from one of the principal image planes. An inclined face will appear foreshortened in two of the principal views and as an edge in the third.
(See 193)
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| independent variable | (n) A variable for which the values are controlled by the experimenter to create a response in the model as measured by the dependent variable. Every independent variable value is paired with one or more dependent variables and represents the experimental manipulation of the model.
(See 206)
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| legend | (n) The region of a visualization where an explanation is given regarding how the variables are coded. This is usually done by equating a text description to a symbol of the code. The legend is also called the key.
(See 206)
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| limiting element | (n) The boundary of the projection of an object. The term is usually used to describe the edge defining the apex of a curved surface.
(See 190)
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| line graph | (n) A visualization technique, usually 2-D, in which line marks are used to indicate trends in data. In a 2-D line graph, the independent variable is represented on the horizontal scale, and the dependent variable is shown on the vertical scale. The line mark represents the mapping of the two variables.
(See 207)
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| marks | (n) The fundamental graphic elements used to encode data in a visualization. Marks can be thought of as graphic primitives and are typically classified as either simple or complex. Simple marks include points, lines, areas, and volumes. Complex marks are also called glyphs. All marks interrelate closely with the dimension of the data type.
(See 204)
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| multiple-line graph | (n) A visualization technique similar to a regular line graph, except that an additional independent variable is mapped. The second independent variable typically has only a few discrete values, each of which is mapped as a separate line on the graph. Color or symbol coding is used to distinguish between the lines on the graph.
(See 209)
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| nominal scale | (n) A qualitative data scale that has no inherent order to it (e.g., New York, Boston, and Houston).
(See 203)
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| normal face | (n) A planar surface of an object that is parallel to one of the principal image planes. A normal face is seen in its true size and shape in the image plane to which it is parallel and is seen as an edge in the other two principal image planes. The normal face is named for the image plane to which it is parallel.
(See 193)
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| oblique face | (n) A planar surface of an object that has been rotated about two axes from one of the principal image planes. An oblique face will appear foreshortened in all three of the principal views. Unlike inclined and normal faces, an oblique face is not seen as an edge in any of the principal image planes.
(See 193)
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| ordinal scale | A qualitative data scale that has an inherent order. Even though ordinal data has an order, the order is not quantitative because the individual data elements are symbolic and have no inherent magnitude.
(See 203)
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| primary axes | (n) Three mutually perpendicular axes representing the primary dimensions of an object. Each of these axes is normal (perpendicular) to one of the primary image planes.
(See 200)
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| qualitative | (adj.) A type of data used as a method of labeling and identifying. Qualitative data are classified as being either nominal or ordinal.
(See 203)
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| range bars | (n) Line or bar marks, such as those used in bar charts, that indicate an interval of variable values. For example, range bars could be used to indicate the period of time that a product is in transit between machining stations on a manufacturing line.
(See 207)
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| reference lines | (n) Lines used to correlate scale values with data markers in a visualization. Because reference lines are not the central focus of a visualization, they tend to be thin and sometimes dotted or dashed.
(See 206)
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| regression line | (n) A line mark used in conjunction with point marks to represent data trends in a visualization. Although this line, either linear or curved, can be drawn freehand, it is usually calculated using statistical techniques.
(See 207)
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| scalar value | (n) A quantitative data type that expresses magnitude but not direction.
(See 203)
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| scale | (n) Ameasuring tool used to calculate distances on a technical drawing. Scale can refer to both the physical tool, similar to a ruler, and the mathematical ratio used to calculate the size difference between the actual object and the drawn representation of the object. Scale lines in a visualization map the scale values to the graphic figure.
(See 206)
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| shape | (n) The internal spatial relationship of vertices and edges that make up a face or the arrangement of faces on an object. Examples of characteristics used to describe a face are the number of edges (sides), the angle between edges, and the ordering of edges around the perimeter. Shape is independent of overall scale but not of viewpoint.
(See 190)
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| single-curved surface | (n) A surface that curves in only one dimension. A cylinder is an example of a single-curved surface. Single-curved surfaces can be developed without distorting or altering the topology of any of the faces.
(See 197)
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| subtractive | (adj. or v) A process or state in which elements are removed from each other. Subtractive is the opposite of additive.
(See 192)
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| surface plot | (n) A 3-D visualization technique used with two independent variables (X and Y) and one dependent variable (Z). A surface connecting the data points represents the mapping of the independent and dependent variables. Shading and other rendering techniques are often used to help visualize the surface.
(See 209)
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| vector value | (n) A quantitative data type that expresses both magnitude and direction.
(See 204)
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2002 McGraw-Hill Higher Education