How do I view initialization (or other invisible) cells in a notebook?

Question

I am looking at someone else's notebook, and when I go to evaluate it, it asks whether I want to evaluate the initialization cells. I would like to look at them first, but "I do not see them here nor there, I do not see them anywhere".

How do I reveal these cells, and, for that matter, any other invisible cells in the notebook? I searched (sought?) for "initialization cell/s" and for "invisible cell/s" in the Wolfram documentation, and only found info about cells that don't have visible cell brackets, no info about cells that are completely invisible. Not how to hide my own or reveal someone else's. I found only this: howto/SelectCellsWithoutVisibleCellBrackets

I'd be grateful for guidance.

Answer 1

The initialization cells are not necessarily invisible.

You can convert any cell to an initialization cell using the relevant menu item:

To find such cells in your colleague's notebook, look for brackets that look like this (this is a magnified version):

The difference from a normal input cell is the little vertical spur coming off the diagonal. I think of this as being an "i" for initialization.

If the cell really is invisible, it means that it does not have the property "Open" as shown in the menu above. But there should be a small bracket visible nonetheless.

If the cell brackets are invisible for all cells, you might need to change something in the Options Inspector (under Cell Options -> Display Options -> CellBracket Options).

Answer 2

Without being able to access the notebook in question, I can't be sure, but my first guess is that you're dealing with a collapsed cell group. Mathematica allows you to collapse a group of cells so that only the first one is visible. This is indicated by the presence of a solid blue arrow on the cell bracket, like this:

To expand the group, just double-click on the bracket, and all the cells will be visible:

Alternatively, you can select everything in the notebook (Edit > Select All) and expand all the cell groups using Cell > Grouping > Open All Subgroups.

If that doesn't work, it's possible that some of the cells themselves are closed. To reveal those, you can select the whole notebook again and then make sure that Cell > Cell Properties > Open is checked.

By the way, whether a cell is visible or not has nothing to do with whether it's an initialization cell. All it means for a cell to be an initialization cell is that Mathematica gives you a chance to have that cell executed automatically before anything else in the notebook is evaluated.