I am curious why you created the new user account yuyu11 in addition to yuyu1.
For both accounts, please follow the advice by jrkrideau. Screen shots are not very useful for the people trying to help you.
You are not using the |> pipe operator properly. The results of the two filters will be piped to the next line as the FIRST argument for the select function. You confuse things by also putting the original mydata in the select function. It will be placed in the next, or SECOND, position and so interpreted by the select function as a column name and mydata is not a column name.