The research field chooses you. Who do you have access to that influences your perspective on the world. I had professors in undergrad who focused on cryptography and security. I did several independent studies in cryptography. That led me to work at a company that worked in cryptography, and programming language design. the job I was put on at that company had me working on programming language design for machine learning. My friend started working in physical oceanography, and gained access to large amounts of acoustic ocean monitoring data. at the same time my dad started asking questions about how to measure light pollution from photographs, pushing me into image processing. I decided to go back to school for machine learning in order to sort out that data. I focused on identifying whale songs and measuring light pollution, pushing me into machine learning for signal processing. Now I work in machine learning research for identifying security vulnerabilities in compiled binaries. My side projects research now is in natural language processing and information retrieval on medical texts. This is because the graduate school I chose happened to be a medical University.