Axis 282 Bedienungsanleitung PDF herunterladen (Seite 16)

Chapter II-12 — Graphs

II-248

The graph can be in one of five modes with respect to each

dimension: auto, absolute, per unit, aspect, or plan. These

modes control the width and height of the plot area of the

graph. The plot area is the shaded area in the illustration.

The width mode and height mode are independent.

In this graph, the axis standoff feature, described in the Mod-

ifying Axes section on page II-264, is off so the plot area

extends to the center of the axis lines. If it were on, the plot

area would extend only to the inside edge of the axis lines.

Auto mode automatically determines the width or height of

the plot area based on the outside dimensions of the graph and other factors that you specify using Igor’s

dialogs. This is the normal default mode which is appropriate for most graphing jobs. The remaining modes

are useful for special purposes such as matching the axis lengths of two or more graphs or replicating a stan-

dard graph or a graph from a journal.

If you select any mode other than auto, you are putting a constraint on the width or height of the plot area

which also affects the outside dimensions of the graph. If you adjust the outside size of the graph, by drag-

ging the window’s size box, by tiling, by stacking or by using the MoveWindow operation, Igor first deter-

mines the outside dimensions as you have specified them and then applies the constraints implied by the

width/height mode that you have selected.

With Absolute mode, you specify the width or height of the plot area in absolute units; in inches, centime-

ters or points. For example, if you know that you want your plot area to be exactly 5 inches wide and 3.5

inches high, you should use those numbers with an absolute mode for both the width and height.

If you want the outside width and height to be an exact size, you must also specify a fixed value for all four

margins. For instance, setting all margins to 0.5 inches in conjunction with an absolute width of 5 inches and

a height of 3.5 inches yields a graph whose outside dimensions will be 6 inches wide by 4.5 inches high.

The Aspect mode maintains a constant aspect ratio for the plot area. For example, if you want the width to be

1.5 times longer than the height, you would set the width mode to aspect and specify an aspect ratio of 1.5.

The remaining modes, per unit and plan, are quite powerful and convenient for certain specialized types of

graphs, but are more difficult to understand. You should expect that some experimentation will be required

to get the desired results.

In Per unit mode, you specify the width or height of the plot area in units of length per axis unit. For exam-

ple, suppose you want the plot width to be one inch per 20 axis units. You would specify 1/20 = 0.05 inches

per unit of the bottom axis. If your axis spanned 60 units, the plot width would be three inches.

In Plan mode, you specify the length of a unit in the horizontal dimension as a scaling factor times the length of

a unit in the vertical dimension, or vice versa. The simplest use of plan scaling is to force a unit in one dimension

to be the same as in the other. To do this, you select plan scaling for one dimension and set the scaling factor to 1.

Until you learn how to use the per unit and plan modes, it is easy to create a graph that is ridiculously small

or large. Since the size of the graph is tied to the range of the axes, expanding, shrinking or autoscaling the

graph makes its size change.

You can also get confusing results if you over-constrain Igor. For example, it is possible to specify that the

width should be 1.5 times the height and that the height should be 1.5 times the width. You should avoid this.

Sometimes you can end up with a graph whose size makes it difficult to move or resize the window. Use

the Graph menu’s Modify Graph dialog to reset the size of the graph to something more manageable.

You may get surprising results when these modes are used in combination with the Fill Page, Custom Size

and Same Aspect radio buttons in the Print Graphs dialog. This is because of interactions between the

effects of the radio buttons and the modes. The Same Size radio button does not cause interaction and there-

fore is the simplest to use.

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Inside Width

Plot Area

Outside Width

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