📄 m34 - generating data with do loops - 32 of 34.mht
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<H2><STRONG><A name=3DText>Text Summary</A></STRONG> </H2>
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<P><STRONG>Purpose of DO Loops</STRONG><BR>DO loops <A=20
onmouseover=3D"window.status=3D'Display details on the uses of DO =
loops.'; "=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_2.htm">process =
groups</A> of SAS statements repeatedly, reducing the number of =
statements=20
required in repetitive calculations. </P>
<P><STRONG>Syntax of Iterative DO Loops</STRONG><BR>To construct =
an=20
iterative DO loop, specify an <A=20
onmouseover=3D"window.status=3D'Display details on DO loop =
syntax.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_3.htm">index=20
variable</A> and the conditions that will execute the loop. These=20
conditions include a start value for the index variable, a stop =
value, and=20
an increment value. Start, stop, and increment values can be any =
number,=20
numeric variable, or SAS expression that results in a number.=20
<P><STRONG>DO Loop Execution</STRONG><BR>During each iteration of =
a DO=20
loop, <A=20
onmouseover=3D"window.status=3D'Display details on DO loop =
executions.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D'';"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_4.htm">new =
values are=20
created</A> in the SAS program data vector. Once the loop's index =
value <A=20
onmouseover=3D"window.status=3D'Display details on DO loop stop =
values.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_4.htm">exceeds =
the stop=20
value</A>, the DO loop stops, and processing continues with the =
following=20
DATA step statement.=20
<P><STRONG>Counting Iterations of DO Loops</STRONG><BR>A simple =
way to=20
track DO loop iterations is to create a temporary counting =
variable, then=20
drop this variable from the data set. Or, <A=20
onmouseover=3D"window.status=3D'Display details on counting DO =
loop iterations.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_7.htm">include =
an OUTPUT=20
statement</A> within the DO loop to write an observation for each=20
iteration. This overrides the automatic generation of output at =
the end of=20
the DATA step.=20
<P><STRONG>Decrementing DO Loops</STRONG><BR>You can decrement a =
DO loop=20
by <A=20
onmouseover=3D"window.status=3D'Display details on decrementing DO =
loops.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
=
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_9.htm">specifying a=20
negative value</A> for the BY clause. The start value must be =
greater than=20
the stop value.=20
<P><STRONG>Specifying a Series of Items</STRONG><BR>You can =
specify how=20
many times a DO loop executes by <A=20
onmouseover=3D"window.status=3D'Display details on specifying a DO =
loop series of items.';"=20
onclick=3DsuggestBack() onmouseout=3D"window.status=3D'';"=20
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_9.htm">listing =
items in=20
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