Chart

The chart of the data makes it possible to facilitate the analysis and the interpretation of these data. Guard should however be taken not to be let misuse by translations of coordinates and graphic sets on the colors, the prospect or the thickness of the features sometimes intended to mask or minimize important information.

The base of the charts is the analytical Geometry.

Layout by a show of hands

Layout of an analytical function of only one variable

When the function has an analytical definition (“formula”) exact, one starts by making a study of the function, i.e. one calculates his Dérivée and his Dérivée second, and one looks at the particular points and directions:

  • discontinuity;
  • direction of variation, defined by the sign of the Derived ;
  • Not of inflection;
  • Not of graining;
  • intersection with the axes;
  • tangent Horizontal E;
  • Asymptotic.

After having traced and having graduated the axes, one places the particular points, one plots the straight lines of asymptote and the tangents remarkable, then by a show of hands, one plots a smooth curve while passing by the point given and respecting the directions.

See the detailed article Study of function.

If the function is too complicated to be studied, one can be satisfied to make a table of values. It is necessary to start by establishing the interval of the layout, which must be centered on the “interesting” zone, for example present of the variations of curve, the particular points, and in general contains the point O (0; 0); that can require to work by test-error.

One selects then a “step of sampling”; for example, one divides the interval into 9 equal parts, and one calculates the values for the 10 points delimiting these parts. When the slope increases, or if a particular point is seen, one can recompute values more tightened “to refine” the layout (local oversampling). One can determine the zeros by Dichotomie.

The points are then deferred in the form of right crosses (+), and one plots the free-hand curve while sticking so that it is smooth.

If one can determine reiterated Dérivées from the function, one can trace the polynomial obtained by Développement limited to the place of the function.

Group of dots

August 1st bars of error

polar diagram, figure of poles

a variable and a parameter (beam of curves)

two variables (or three dependant variables): level lines, triangular diagram (ternary cf diagram)

Statistical diagrams

August 1st Camembert cheese, bars, population pyramid

See also: Charts of statistical data

Data-processing layout

August 1st layout 2D, 3D, chart in levels of gray

numerical Interpolation, Smoothing

See too

Related articles

External bonds

  • Year Introduction to PSTricks: Plotting dated (p18): layout of function in Latex

  • How to lie with graphs: techniques to know not to let itself misuse.
  • Document pdf on the same subject
  • FooPlot: to trace graphs of functions in line

Works

  • Bertin, graphic Semiology

  • Darrell Huff, How to binds with statistics

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