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GRAPHICAL METHODS

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Originally appearing in Volume V12, Page 364 of the 1911 Encyclopedia Britannica.

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GRAPHICAL METHODS , devices for representing by geometri-' cal figures the numerical data which result from the quantitative investigation of phenomena. The simplest application is met with in the See also:

REPRESENTATION

representation of See also:

TABULAR

tabular data such as occur in See also:

STATISTICS

statistics. Such tables are usually of single entry, i.e. to a certain value of one variable there corresponds one, and only one, value of the other variable. To construct the graph, as it is called, of such a table, Cartesian co-ordinates are usually employed. Two lines or axes at right angles to each other are chosen, intersecting at a point called the origin; the See also:

HORIZONTAL

horizontal See also:

AXIS (Lat. for " axle ")

axis is the axis of abscissae, the See also:

VERTICAL (from Lat. vertex, highest point)

vertical one the axis of ordinates. Along one, say the axis of abscissae, distances are taken from the origin corresponding to the values of one of the variables; at these points perpendiculars are erected, and along these ordinates distances are taken corresponding to the related values of the other variable. The See also:

CURVE (Lat. curvus, bent)

curve See also:

DRAWN

drawn through these points is the graph. A See also:

general inspection of the graph shows in bold See also:

RELIEF

relief the essential characters of the table. For example, if the See also:

WORLD

world's See also:

PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of See also:

corn over a number of years be plotted, a poor yield is represented by a depression, a See also:

rich one by a See also:

PEAK, THE

peak, a See also:

UNIFORM

uniform one over several years by a horizontal See also:

LINE

line and so on. Moreover, such graphs permit a convenient comparison of two or more different phenomena, and the curves render apparent at first sight similarities or See also:

DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences which can be made out from the tables only after See also:

close examination. In making graphs for comparison, the scales chosen must give a similar range of variation, otherwise the See also:

correspondence may not be discerned. For example, the scales adopted for the See also:

AVERAGE

average See also:

CONSUMPTION (Lat. consumere)

consumption of See also:

TEA (Chinese cha, Amoy dialect t€)

tea and See also:

SUGAR

sugar must be ounces for the former and pounds for the latter.

Cartesian graphs are almost always yielded by automatic recording See also:

INSTRUMENTS

instruments, such as the barograph, meteorograph, See also:

SEISMOMETER (from Gr. veurp6s, earthquake, and µfpov, a measure)

seismometer, &c. The method of polar co-ordinates is more rarely used, being only specially applicable when one of the variables is a direction or recorded as an See also:

ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle. A See also:

SIMPLE

simple See also:

case is the representation of photometric data, i.e. the value of the intensity of the See also:

LIGHT

light emitted in different directions from a luminous source (see See also:

LIGHTING

LIGHTING). The geometrical See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution of arithmetical and algebraical problems is usually termed graphical See also:

ANALYSIS (Gr. avci and Meta, to break up into parts)

analysis; the application to problems in See also:

MECHANICS

mechanics is treated in MECHANICS, § 5, Graphic See also:

STATICS (from Gr. root am-, stand, or cause to stand)

Statics, and See also:

DIAGRAM

DIAGRAM. A See also:

SPECIAL

special phase is presented in VECTOR ANALYSIS.

End of Article: GRAPHICAL METHODS

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