Page:Graphic methods for presenting facts (1914).djvu/278

 In Fig. 205 a curve is shown drawn upon a carefully designed four-by-six-inch card form. This card is designed for the plotting of data for one year by months. Thus, the fiscal year of a business can be shown on one card. Succeeding years are entered on different cards, so that by arranging the cards chronologically variations from year to year may easily be seen. In order to avoid the difficulties pointed out for Fig. 204, and Fig. 104, thirteen vertical lines are used on this four-by-six-inch card. At the beginning of each card the last month of the previous fiscal year is repeated. In Fig. 205 the fiscal year begins in August. At the beginning of the card we repeat the line for July, so that instead of showing a dot when the August figures are plotted we are able to draw a line showing the change which has occurred from July to August. In general, it is good practice to use one more vertical line than there are points to be plotted, so that the last point on one curve, sheet or card may be repeated on the next curve sheet or card.

Figures representing the value for each point on the curve are given immediately above each point, in the case of Fig. 205 to the nearest dollar. Figures for cents could, of course, be given if desired, but for executive purposes it is usually better to neglect the cents in all large numbers. The arrangement of the figures shown in Fig. 205 is such that at the end of the year the figures can be added quickly and the total given on the card. Cards for different years can easily be looked over and the yearly total figures compared instantly, to the great advantage of the executive who has these additions made for him and recorded where they are always in plain sight. Curves as they were used in the past gave the values of single points only, without any summation for a series of points. In Fig. 205 we have not only the yearly total, but also totals for every three months, so that the total for any quarter of the fiscal year can be compared with the total for any other quarter.

Fig. 206 represents a four-by-twelve-inch card used to plot data for fifty-two weeks in one fiscal year, the last point of the preceding year being repeated at the left-hand margin. Figures for the repeated week are not given above the co-ordinate ruling, as the repeated figures might then be included in the additions and cause serious error. By repeating the point, however, and not repeating the figures, the curve is made continuous without any danger of adding too many items into the total.

In the right-hand margin of Fig. 206 a short vertical line may be seen. This line may be used as the shank of an arrow to indicate, as