How is the default for the checkboxes created by
CheckboxBar in a
Manipulate set to be checked instead of unchecked? (The number of checkboxes may be variable.)
You can specify an initial value to a variable captured by a Manipulate construct. In your particular case, you could do something like this:
This creates a CheckboxBar control with five checkboxes all preset to the checked state. The values in the CheckboxBar do not need to be integers.
will produce the following initial state when evaluated.