sum和+之间的区别? [英] sas difference between sum and +?

问题描述

data whatever;
 infile '';
 input price cost;
 <statement>;
run;

在中，使用total = sum(total,cost)和total = total + cost有什么区别?

In <statement>, what's the difference between using total = sum(total,cost) and total = total + cost ?

推荐答案

区别如下:

如果你想计算累计总数，你应该使用 sum 语句.

If you want to calculate cumulative total , you should use sum statement.

total = sum(total,cost)/* 它是一个求和函数 */

total = sum(total,cost) /* its a sum function */

total+cost/* 求和语句，形式为变量+表达式*/

total+cost /* its a sum statement,the form is variable+expression */

这里:

total"指定累加器变量的名称，其中包含一个数值.

"total" specifies the name of the accumulator variable, which contains a numeric value.

1) 在 SAS 读取第一个观测值之前，变量(在这种情况下为总计)自动设置为 0.变量的值从一个迭代保留到下一个迭代，就好像它出现在 RETAIN 语句中一样.

1) The variable(total in this case) is automatically set to 0 before SAS reads the first observation. The variable's value is retained from one iteration to the next, as if it had appeared in a RETAIN statement.

2) 要将 sum 变量初始化为 0 以外的值，请将其包含在具有初始值的 RETAIN 语句中.

2) To initialize a sum variable to a value other than 0, include it in a RETAIN statement with an initial value.

和

成本"是一个表达式

1) 计算表达式并将结果添加到累加器变量中.

1) The expression is evaluated and the result added to the accumulator variable.

2) SAS 将产生缺失值的表达式视为零.

2) SAS treats an expression that produces a missing value as zero.

sum 语句与 sum 函数的不同之处在于 sum 语句保留了它之前计算的值.

A sum statement is differ from a sum function in a way that a sum statement retains the value which it has calculated earlier.

然而，sum 语句相当于使用 SUM 函数和 RETAIN 语句，如下所示:

However, The sum statement is equivalent to using the SUM function and the RETAIN statement, as shown here:

retain total 0;
total=sum(total,cost);

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