BY vs CLASS

[souji]

Hi

In which instant I can use BY or CLASS in the Proc Means procedure

 in SAS prep guide, Scenario 7, they asked to:

　

Use PROC MEANS to calculate the mean and standard deviation for the variables AvgHighTemp and AvgLowTemp by the new Month variable.

In the code they use CLASS instead of BY

Q: How do I know when to use CLASS or BY, Please help me to understand

data work.scenario7;

set cert.temp18;

format Day date9.;

Month=month(day);

run;

proc freq data=work.scenario7;

tables HighTemp;

run;

proc means data=work.scenario7; 

class month;

var AvgLowTemp AvgHighTemp;

run;

[unison]

Rick has a wonderful article on this: https://blogs.sas.com/content/iml/2018/02/14/difference-class-and-by-statements-sas.html