Are the verb and noun omissions in the following sentence correct? (The words enclosed in parentheses are the omitted ones.)
The bottom graph shows the acceleration profiles, while the top (graph) (shows) the corresponding speed changes.
All three of Edwin Ashworth's suggestions (in his comment above) are quite sound, although I would use a semicolon after the first phrase in the first and second options to make clearer what the remaining comma in each case is doing:
The bottom graph shows the acceleration profiles; the top, the corresponding speed changes.
The bottom graph shows the acceleration profiles; the top graph, the corresponding speed changes.
The bottom graph shows the acceleration profiles, while the top graph shows the corresponding speed changes.
Also sound is Kris's suggestion (also above), which I like because it adopts upper and lower in place of top and bottom—a gentle nod to the fact that the caption is dealing with two graphs, not three or more. (I should note that top and bottom aren't wrong in this situation, any more than best and worst are in a comparison of two pies; but just as better and worse are all you need for complete identification of the relative merits of the pies, upper and lower are all you need for complete location information for the two graphs.) Kris suggests this formulation:
Lower graph shows acceleration profiles; Upper graph shows corresponding speed changes.
I'm not sure why upper is capitalized after the semicolon—I would either replace the semicolon with a period or lowercase the u in upper—but the wording is fine otherwise. Another way of telescoping the information to fit a narrow caption space is to put the graph identifications in parentheses and dispense with verbs altogether:
Acceleration profiles (lower graph) and corresponding speed changes (upper graph).
This approach is very useful in situations where your caption can't exceed a severely limited character count. If even that shortening doesn't put you under the character limit (assuming that you have one), you can resort to dropping the second occurrence of the word graph:
Acceleration profiles (lower graph) and corresponding speed changes (upper).