May I explain the sentence a little more. My(Determiner,the possessive form of I) main (Adjective which explains the noun Duty) duty (Noun ) is (verb) to(infinitive marker) Analyze(Infinitive,The basic form of a verb) data(noun) to identify(infinitive) system(here it is used as adjective for the noun errors) errors(noun) and (conjunctive) then(adverb, which is used to describe the verb correct