How to plot Topics' triggetings

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Hi all, I want chart/graph to to see at which time whicht topic triggered. e.g I have a topic t1 which bublishes strings "yes" and sometimes "no". Another topic t2 publishes string "why" only when t1 bublishes "no". Now I want to get a chart/graph. When and which topic triggered. I have seen the rxplot (only works for numeric values). rxconsole gives the output but in a seraial form. Is there any way you know how to get my desired plot OR how to get a text file from rxconsole so that i can play with in Matlab to get the plot. I mean I am only interested triggering of the topic but on some specific values. Any clues please? Thanks in advance