I have another issue in relation to keeping variables with a joint condition. I am trying to select banks with particular criteria Total assets greater 40B for example for each quarter. But of cause, Bank A may have >40b in quarter one and quarter two of the same year it does not meets the criteria. However, I will like to keep the bank irrespective of the quarter and year as long as it meets the criteria. I have done the following but unable to link the two conditions. 1) by BANKID generate available =0, replace available=1 if Totalassets >=40B, based on the condition those with zero may at some time have 1; so using keep if available ==1 will not work. can you help me with how to specify the condition of =1 & 0 so it will capture both lines? Simply put, to keep banks with total assets >=40B at any period and remove those <40B all through the years.

Bankid date net income interest expense Total assets
102223 1991Q1 54034 235890 45000
102223 1991Q2 45000 7067 45000
102223 1991Q3 54034 80004 45000
102223 1991Q4 23700 345000 45000
102223 1992Q1 . 7800 .
102223 1992Q2 120000 6000 .
102223 1992Q3 85000 . .
102223 1992Q4 85000 . .
102223 1993Q1 85000 . .
102223 1993Q2 85000 . .
102223 1993Q3 85000 . .
102223 1993Q4 85000 . .
102224 1994Q1 85000 . 75000
102224 1994Q2 85000 . 75000
102224 1994Q3 . . 75000
102224 1994Q4 . . 75000
102224 1995Q1 . . 68000
102224 1995Q2 . . 68000
102224 1995Q3 . . 68000
102224 1995Q4 . . 68000