Axis 282 Bedienungsanleitung PDF herunterladen (Seite 30)

Chapter II-12 — Graphs

II-262

When offsetting a trace that uses log axes, the trace offsets by the same distance it does when the axis is not

log. The shape of the trace is not changed — it is simply moved. If you were to try to offset a trace by adding

a constant to the wave’s data, it would distort the trace.

Trace Multipliers

In addition to offsetting a trace, as of Igor Pro 6, you can also provide a multiplier to scale a trace. The effec-

tive value used for plotting is then multiplier*data+offset. The Trace Offset subdialog also contains entries for

the multiplier. Note that the default value of zero means that no multiplier is provided — not that the data

should be multiplied by zero.

You can interactively scale a trace using the same click and hold technique described for trace offsets. But

first, you must place Cursor A somewhere on the trace to act as a reference point. Then, after entering offset

mode, you can press Option (Macintosh) or Alt (Windows) to adjust the scaling. You can press and release

the key as desired to alternate between scaling and offsetting.

The trace multiplier feature is an alternative method of offsetting a trace on a log axis (remember:

log(a*b)=log(a)+log(b)). For compatibility reasons and because the trace offsets method better handles switching

between log and linear axis modes, the multiplier method applies when interactively dragging a trace only if the

offset is zero and the multiplier is not zero (the default meaning “not set”). Consequently, to use the new tech-

nique, you must use the command line or the Trace Offset subdialog to set a nonzero multiplier (1 can be used).

Hiding Traces

You can hide a trace in a graph, without removing the trace from the graph or by changing any other prop-

erties of the trace, by selecting the Hide Trace checkbox in the Modify Trace Appearance dialog. When you

hide a trace, you can use the Autoscale checkbox to control whether or not the data of the hidden trace

should be used when autoscaling the graph.

Complex Display Modes

When displaying traces for complex data you can use

the Complex Mode pop-up menu to control how the

data are displayed. You can display the complex and

real components together or individually, and you can

also display the magnitude or phase.

The default display mode is Lines between points. To display a wave’s real and imaginary parts side-by-

side on a point-for-point basis, use the Sticks to zero mode.

Gaps

In Igor, a missing or undefined value in a wave is stored as the floating point value NaN (“Not a Number”).

Normally, Igor shows a NaN in a graph as a gap, indicating that there is no data at that point. In some cir-

cumstances, it is preferable to treat a missing value by connecting the points on either side of it.

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3.02.52.01.51.00.50.0

real and imaginary parts using

Sticks to zero display mode

Point 4 real part

Point 4 imag part

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