I´m a beginner working with a huge dataset where I want to tidy/sort my data. My dataset contains 150 variables and 1000 observations. My first question is: One of my variables is named "dia1" and contains codes, such as DKZ455. First I want to just include observations where "dia1" starts with "DK*".
My second aim is to include only observations where "dia1" equals a specific value noted on a list containing about 100 different values, DKZ455, DKJ044 etc. If not on the list it shall not show.