```Date: Wed, 22 May 1996 13:51:38 GMT Reply-To: Zhongwen Lai Sender: "SAS(r) Discussion" From: Zhongwen Lai Organization: University of Pennsylvania Subject: Re: help of sum. in SAS programming Some one posted a programming question (as follows) but I lost the after I first quit the newgroup thus his/her name and email address. So I have to post my answer to the group and hope he/she can read it. QUESTION Suppose there is a variable X in SAS data set Q, with its values denoted as x1, x2, ..., xn from the first obs to the last obs n, how to construct a new variable Y which is defined as follows: X Y x1 y1=x1 x2 y2=x1+x2 (=y1+x2) x3 y3=x1+x2+x3 (=y2+x3) . . . xn yn=x1+x2+,,,+xn (=y(n-1)+xn) ANSWER Y can also be expressed in the form of the third column, so the answer is simple: DATA A; SET Q; RETAIN Y; Y=Y+X; RUN; This logic, in combination with FIRST.var and LAST.var, where var is the variable by which the data is sorted (e.g, var is a ID variable for each individual and each individual may have multiple obs in the data set), you can also obtain the SUM of a given variable for each individual, or simply count the number of occurences. Zhongwen Lai at Upenn ```

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