2 Calculated fields should do it, 1 for Trump and 1 for Clinton:
TRUMP: IF CONTAINS([TweetField],'Trump') THEN 1 END
CLINTON: IF CONTAINS([TweetField],'Clinton') THEN 1 END
You can then just sum those fields to give the counts. They can be trended on a line chart using the Measure Names/Measure Values way of charting.
Thanks Andrew. That does do it. And that shows me how to create a line for each search I'd like to do.
A couple of follow up questions, if I may:
1) Are those case-sensitive? (i.e. does Trump also find trump and TRUMP)
2) Is there a way of having a search box that just dynamically shows volume without create a new measure each time?
Yes it is case sensitive. What you can do is create parameter so that the user would enter a value then use the following calculated field :
IF CONTAINS(UPPER([TweetField]),UPPER([Parameter])) THEN 1 END
Marc is correct, it's case sensitive so, to break into stages, to account for case sensitivity you can change your formula to:
TRUMP: IF CONTAINS(UPPER([TweetField]),'TRUMP') THEN 1 END
To create a parameter to allow the user to have a search box you can see how to do that at this link: Using Parameters to search a free text field ~ Wannabe Data Rock Star
Marc's formula is the correct one to work with the parameter.
Thanks folks. Really helpful!