Page:Graphic methods for presenting facts (1914).djvu/16

Chapter V. Curve Plotting 69

The desirability of using only well-known methods of presentation.
Curves permit a more rapid and more accurate interpretation than possible
by other methods. Studies of the causes of crests and valleys of curves.
Curves especially needed for complex data. The use of curves in advertising.
Polar co-ordinates objectionable for presenting statistical data. Examples
of good practice in curve plotting.


Chapter VI. Curve Plotting Continued 84

Independent and dependent variables. Confusion caused if the independent
variable is not used for the horizontal scale. Examples showing
correct arrangement of scales. Curves to advertise newspaper circulation.
Curve charts combining much complex information. The use of two sets of
co-ordinate ruling for the vertical scale. Moving averages. Smoothing
curves. Index numbers. Weighted averages. Curve studies of national
prosperity.


Chapter VII. Comparison of Curves 107

Similarity and contrast of curves plotted in the same field. The zero
of the vertical scale should be shown on the chart. Advantages of plotting
curves for different years one above the other for comparison. Contrast
in shape of curves plotted in separate fields. Advantage from shading the
space under a curve. Numerous dissimilar but related curves on the same
sheet. Errors resulting if curves not having the same zero line are compared.
A total curve plotted from several other curves. Inverse relations, one curve
trending downward when another trends upward. Study of correlation
by plotting a curve from the data of two other curves. The angle of a curve
on ordinary rectangular co-ordinates tells nothing about the percentage rate
of growth. Disadvantages of the arithmetical scale ruling for curve
plotting. Advantages obtained by plotting curves on logarithmically ruled
paper.


Chapter VIII. Component Parts Shown by Curves 138

Use of vertical bars with components totalling 100 per cent. Shaded
area under a curve when the height of the total field represents 100 per
cent. The use of several areas in a curve field which totals 100 per cent.
in height. A contrasting method of showing all curves plotted separately
but from the same zero line. Universal co-ordinate paper for convenience
in curve plotting. Total curves with component areas so that any point on
a curve totals 100 per cent for the height of the areas beneath.


Chapter IX. Cumulative or Mass Curves 149

Factory production schedules and actual outputs plotted on a cumulative
basis. Curves for income and expense on a cumulative basis. Various uses
for cumulative curves. Cumulative curves with lines drawn to show rate