Extra Axis

By default, graphs contain an x and y axis with tick marks and ranges that are automatically generated based on the data selected in the drawing command.

The Axis settings have a number of ways to customize the axes, but when you need more customization, add an Extra axis command.

Add an Extra Axis

You can add an extra axis drawing command using the Command menu.

The Extra Axis can be placed anywhere on the graph. Use this command to:

• Customize the look and location of the axis,
• Convert the axis units without modifying data, or
• Add a second axis.

Replace the Axis

You can use the extra axis to replace the default scale on the x or y axis. In the Axis commands, hide the default axis by unchecking ‘Draw x/y numbers’.

NOTE: You don’t have to remove the default axis. You can combine several Extra Axis commands, and continue to show the default.

Type

You can move the extra axis to the y-axis by using the Type drop-down box.

Units

Use the Extra axis as a way to display in different units on the axes, without having to change the data.

Conversion Factors

To have a custom conversion, enter numerical values directly into the Data and Display entry boxes.

Axis units are multiplied by numbers entered into the Data field, and are divided by numbers entered into the Display field multiplied

Symbolic Units

DataGraph contains a large number of built-in units to allow you to convert between units symbolically.

1. Change the Units drop-down box to ‘Convert’.
2. Enter the units of your data (Data)
3. Enter the units you want to show (Display)

For example, here is an Extra Axis command set to convert from centimeters to meters.

Some of the constants have more than one symbol defined. For example, gallon can be understood as ‘gal’, ‘gallon’, or ‘gallons’. If you enter a symbol that is not defined a warning will be displayed that lists all of the symbolic constants that have been defined.

You can think of each of these constants as built-in variables that represent a conversion factor based on SI units. For example, the value for meters ‘m’ is one since meters is the SI unit for length. The value for ‘cm’ is 0.01 since cm is one-one hundredth of the meter. The conversion of the data is done by multiplying by the ratio of Data/Display to show the requested units.

Note: DataGraph will not warn you if you pick a combination of units that don’t make physical sense (i.e., converting from volume to mass). The full list of constants is included in the appendix.

Position

You can also set up multiple scales on the same axis using the position offset.

Range

The Range limits the section of the axis that is drawn.

By default the range is unlimited (-∞, ∞).

You can limit the lower bound (10, ∞), upper bound (-∞, 15) , or limit both.

If you delete the infinity symbol (∞) and later decide you would like to use that setting, type Option-5 on the keyboard.

NOTE: This setting does not change the range that is included in the graph (that is controlled in the Axis settings).

Exclude

Exclude the tick mark label being drawn at a value or a comma separated list of values.

Prefix, Suffix

Add a prefix or suffix to all the tick mark labels.

Labels

Labels for the y-axis are added above the axis.

Font & Line

You can control the font style and color, as well as, the color of the axis line.

Drawing Style

You can customize how the axis is drawn.

For example, here the Extra axis command is used to add tick marks to a graph with a Split Y Axis, where the Drawing style is ‘Only ticks’.

Major Grid & Minor Grid

Add a grid the corresponds to the extra axis tick marks.

Space for y

Changes the amount of space reserved for the tick mark labels. If these numbers are long, you may need to increase.

Room at ends

Moves the tick mark labels at the end of the axis.