Axis 282 Uživatelský manuál stáhnout pdf (Strana 53)

Chapter II-12 — Graphs

II-285

The Character hierarchical menu presents a table from which you can select text and special characters to

add to the axis label.

The Marker hierarchical menu inserts a code to draw a marker symbol. These symbols are independent of

any traces in the graph.

The items in the Units pop-up menu insert escape codes as shown here:

These codes allow you to create an axis label that automatically changes when the extent of the axis changes.

For example, if you specified units for the controlling wave of an axis you can make those units appear in

the axis label by choosing the Units item from the Units pop-up menu. If appropriate Igor will automatically

add a prefix (µ for micro, m for milli, etc.) to the label and will change the prefix appropriately if the extent

of the axis changes. The extent of the axis changes when you explicitly set the axis or when it is autoscaled.

If you are plotting a waveform (wave’s Y values plotted versus its X values) then the units for the Y axis come

from the wave’s data units and the units for the X axis come from the wave’s X units. However, if you are plot-

ting an XY pair (Y values of one wave plotted versus Y values of another wave) then the units for the Y axis come

from the data units of one wave and the units for the X axis come from the data units of the other wave.

If you choose the Scaling or Inverse Scaling items from the Units pop-up menu, Igor will automatically add

a power of 10 scaling (x10^3, x10^6, etc.) to the axis label if appropriate and will change this scaling if the

extent of the axis changes. The Trial Exponent buttons determine what power is used only in the label

preview so you can see what your label will look like under varying axis scaling conditions. Both of these

techniques can be ambiguous — it is never clear if the axis has been multiplied by the scale factor or if the

units contain the scale factor.

A less ambiguous method is to use the Exponential Prefix escape code. This is identical to the Scaling code except

the “x” is missing. You can then use it in a context where it is clear that it is a multiplier of units. For example, if

your axis range is 0 to 3E9 in units of cm/s, typing “Speed, \ucm/s” would create “Speed, 10

cm/s”.

It is common to parenthesize scaling information in an axis label. For example the label might say “Joules

(x10

)”. You can do this by simply putting parentheses around the Scaling or Inverse Scaling escape codes.

If the scaling for the axis turns out to be x10

Igor omits it and also omits the parentheses so you get “Joules”

instead of “Joules (x10

)” or “Joules()”.

If you do not specify scaling but the range of the axis requires it, Igor labels one of the tick marks on the axis

to indicate the axis scaling. This is an emergency measure to prevent the graph from being misleading. You

can prevent this from happening by inserting the Manual Override escape code, \u#2, into your label. No

scaling or units information will be printed at the location of the escape code (or on the tick marks). You

will need to provide your own units or scaling by creating an annotation (Chapter III-2, Annotations) or a

simple text object (Chapter III-3, Drawing).

The following four examples illustrate what happens when the axis label does not contain any scaling or

units escape codes:

\u#2

\u#1

1.00.80.60.40.20.0

axis label

Axis range: 0..1 ; Wave units: none ; Axis label text: axis label

1 2 ... 48 49 50 51 52 53 54 55 56 57 58 ... 79 80

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