6) Explain about below automatic variables
a) _N_
b) _ERROR_
c) _CHAR_
d) _NUMERIC_
e) _ALL_
f) FIRST.BY VARIABLE
g) LAST.BY VARIABLE
h) _NAME_
i) _TYPE_
j) _FREQ_
k) _STAT_
l) _BREAK
Automatic variables are created automatically in the data statements and they are added to the PDV but not ouput to
to the resulting dataset which we want.
1)_N_ : number of times the data step has iterated. initially it is 1 and it's counter increases +1 , every time data steps crosses the data statements.
2)_ERROR_: It is 0 by default but is set to 1 every time
the error is encountered.
3)_CHARACTER_ : could be defined in the arrays and other data step programming to include all the character variables.
4)_NUMERIC_ : To include all the numeric variables
5)First.by variable and LAST.By : Whenever, we define a BY parameter with the SET statement, by default two
automatic variables are created in the background and we can utilize them for limiting the rows which we are interested in . {http://support.sas.com/documentation/cdl/en/lrcon/62955/HTML/default/viewer.htm#a000761931.htm}
7) _NAME_ : During transpose the variables you define in VAR statment are transposed and they comes in _NAME_ variable.
proc transpose data=x out=y prefix=m;
by variable1;
id variable2;
var variable3;
run;
8)_TYPE_ and _FREQ_: When you use PROC SUMMARY or PROC MEANS and we define Class parameter for two variables, and we use CHARTYPE in our Proc summary options, then
we get two automatic variables _TYPE_ and _FREQ_ . We can utilize it to limit the output we need.
9)_STAT_ :The default output of PROC MEANS, when no statistics are listed in the OUTPUT statement, is a data set containing a _STAT_ variable and the variables listed in the VAR statement. The output data set contains five records, one for each default statistic N, MIN, MAX, MEAN, and STD.
10) _BREAK_ : PROC report automatically create a variable
_BREAK_.
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