m34 - generating data with do loops - 32 of 34.mht

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      a series</A>; the DO loop will execute once for each item, with =
the index=20
      variable equal to the value of each item. A series can consist of =
all=20
      numeric values, all character values (enclosed in quotation =
marks), or all=20
      variable names (without quotation marks).=20
      <P><STRONG>Nesting DO Loops</STRONG><BR>DO loops can run <A=20
      onmouseover=3D"window.status=3D'Display details on nesting DO =
loops.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D'';"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_13.htm">within =
DO=20
      loops</A>, as long as you assign a unique index variable to each =
loop and=20
      terminate each DO loop with its own END statement.=20
      <P><STRONG>Iteratively Processing Data That Is Read from a Data=20
      Set</STRONG><BR>You can use a DO loop to <A=20
      onmouseover=3D"window.status=3D'Display details on reading data =
with DO loops.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D'';"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_16.htm">read a =
data=20
      set</A> and compute the value of a new variable. DO loop start and =
stop=20
      values, for example, can be read from a data set.=20
      <P><STRONG>Conditionally Executing DO Loops</STRONG><BR>The <A=20
      onmouseover=3D"window.status=3D'Display details on the DO UNTIL =
statement.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_19.htm">DO =
UNTIL</A>=20
      statement executes a DO loop until a condition is true. Because =
the=20
      expression is not evaluated until the bottom of the loop, a DO =
UNTIL loop=20
      will execute at least once. The <A=20
      onmouseover=3D"window.status=3D'Display details on the DO WHILE =
statement.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_23.htm">DO =
WHILE</A>=20
      statement is used to execute a DO loop while a condition is true. =
Because=20
      the DO WHILE statement is evaluated at the top of the DO loop, if =
the=20
      expression is false the first time it is evaluated, the DO loop =
never=20
      executes.=20
      <P><STRONG>Using Conditional Clauses with the Iterative DO=20
      Statement</STRONG><BR>DO WHILE and DO UNTIL statements can be used =
within=20
      iterative DO loops to combine <A=20
      onmouseover=3D"window.status=3D'Display details on conditional DO =
loop clauses.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_27.htm">conditional =
and=20
      unconditional</A> execution.=20
      <P><STRONG>Creating Samples</STRONG><BR>DO loops provide an easy =
way to <A=20
      onmouseover=3D"window.status=3D'Display details on creating =
samples.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_30.htm">create =

      samples</A> from other data sets. Enclose the SET statement in a =
DO loop,=20
      using the start, stop, and increment values to select the =
observations.=20
      Add the POINT=3D option to the SET statement, setting it equal to =
the index=20
      variable of the DO loop. Then add a STOP statement to prevent DATA =
step=20
      looping, and add an OUTPUT statement to write DATA step output.=20
  </P></TD></TR></TBODY></TABLE><!-- InstanceEndEditable --><BR>
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<P><!-- InstanceBeginEditable name=3D"syntax" -->
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    <TD><STRONG><A name=3DSyntax>Syntax</A></STRONG>=20
      <P><EM>To go to the page where a statement or option was =
presented, select=20
      a link.</EM> </P></TD></TR></TBODY></TABLE><BR></CENTER>
<P align=3Dcenter>
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      <DL>
        <DT><FONT color=3D#003399><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"><STRONG>DO</ST=
RONG>=20
        <EM>index-variable</EM>=3D<EM>start</EM> <STRONG>TO</STRONG> =
<EM>stop</EM>=20
        <STRONG>BY</STRONG> =
<EM>increment</EM><STRONG>;</STRONG></A></FONT>=20
        <DD><FONT color=3D#003399><EM>SAS statements</EM></FONT>=20
        <DT><FONT color=3D#003399><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"><STRONG>END;</=
STRONG></A></FONT>=20
        <BR><BR>
        <DT><FONT color=3D#003399><A=20
        onmouseover=3D"window.status=3D'Display details on the DO UNTIL =
statement.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_19.htm"><STRONG>DO=20
        UNTIL(</STRONG><EM>expression</EM><STRONG>);</STRONG></A></FONT> =

<BR><BR>
        <DT><FONT color=3D#003399><A=20
        onmouseover=3D"window.status=3D'Display details on the DO WHILE =
statement.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_23.htm"><STRONG>DO=20
        WHILE(</STRONG><EM>expression</EM><STRONG>);</STRONG></A></FONT> =

<BR><BR>
        <DT><FONT color=3D#003399><A=20
        onmouseover=3D"window.status=3D'Display details on conditional =
DO loop clauses.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_27.htm"><STRONG>DO</S=
TRONG>=20
        <EM>index-variable</EM>=3D<EM>start</EM> <STRONG>TO</STRONG> =
<EM>stop</EM>=20
        <STRONG>BY</STRONG> <EM>increment</EM>=20
        =
<STRONG>UNTIL(</STRONG><EM>expression</EM><STRONG>);</STRONG></A></FONT> =

        <BR><BR>
        <DT><NOBR><FONT color=3D#003399><A=20
        onmouseover=3D"window.status=3D'Display details on conditional =
DO loop clauses.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m34/m34_27.htm"><STRONG>DO</S=
TRONG>=20
        <EM>index-variable</EM>=3D<EM>start</EM> <STRONG>TO</STRONG> =
<EM>stop</EM>=20
        <STRONG>BY</STRONG> <EM>increment</EM>=20
        =
<STRONG>WHILE(</STRONG><EM>expression</EM><STRONG>);</STRONG></A></FONT><=
/NOBR>=20
        </DT></DL></TD></TR></TBODY></TABLE>
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    </TD></TR></TBODY></TABLE><BR></CENTER><!-- InstanceEndEditable -->
<P><!-- InstanceBeginEditable name=3D"sampleprogram" -->
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    <TD align=3Dleft><STRONG><A name=3DSample>Sample =
Programs</A></STRONG>=20
      <BLOCKQUOTE><STRONG>Simple DO Loop =
</STRONG></BLOCKQUOTE><PRE><FONT color=3D#003399>     data =
work.earn;</FONT>
<FONT color=3D#003399>        Value=3D2000;</FONT>
<FONT color=3D#003399>        do year=3D1 to 20;</FONT>
<FONT color=3D#003399>           Interest=3Dvalue*.075;</FONT>
<FONT color=3D#003399>           value+interest;</FONT>
<FONT color=3D#003399>        end;</FONT>
<FONT color=3D#003399>     run;</FONT></PRE>
      <BLOCKQUOTE>
        <P><STRONG>Nested DO Loops </STRONG></P></BLOCKQUOTE><PRE><FONT =
color=3D#003399>     data work.earn;</FONT>
<FONT color=3D#003399>        do year=3D1 to 20;</FONT>
<FONT color=3D#003399>           Capital+2000;</FONT>
<FONT color=3D#003399>           do month=3D1 to 12;</FONT>
<FONT color=3D#003399>              Interest=3Dcapital*(.075/12);</FONT>
<FONT color=3D#003399>              capital+interest;</FONT>
<FONT color=3D#003399>           end;</FONT>
<FONT color=3D#003399>        end;</FONT>
<FONT color=3D#003399>     run;</FONT></PRE>
      <BLOCKQUOTE>
        <P><STRONG>Conditional Clause</STRONG> =
</P></BLOCKQUOTE><PRE><FONT color=3D#003399>     data =
work.invest(drop=3Di);</FONT>
<FONT color=3D#003399>        do i=3D1 to 10 =
until(Capital&gt;=3D50000);</FONT>
<FONT color=3D#003399>           Year+1;</FONT>
<FONT color=3D#003399>           capital+2000;</FONT>
<FONT color=3D#003399>           capital+capital*.10;</FONT>
<FONT color=3D#003399>        end;</FONT>
<FONT color=3D#003399>     run;</FONT></PRE>
      <BLOCKQUOTE>
        <P><STRONG>Creating Samples</STRONG> </P></BLOCKQUOTE><PRE>     =
<FONT color=3D#003399>data work.subset;</FONT>
        <FONT color=3D#003399>do sample=3D10 to 5000 by 10;</FONT>
           <FONT color=3D#003399>set factory.widgets =
point=3Dsample;</FONT>
           <FONT color=3D#003399>output;</FONT>
        <FONT color=3D#003399>end;</FONT>
        <FONT color=3D#003399>stop;</FONT>
     <FONT color=3D#003399>run;</FONT></PRE>
      <HR>
    </TD></TR></TBODY></TABLE><BR><!-- InstanceEndEditable -->
<P><!-- InstanceBeginEditable name=3D"pointstoremember" -->
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    <TD align=3Dleft><STRONG><A name=3DPoints>Points to =
Remember</A></STRONG> <BR>
      <UL>
        <LI>If you do not specify a BY clause, the increment value for =
DO loops=20
        is 1.<BR><BR>
        <LI>In most cases, the index variable is needed only for =
processing the=20
        DO loop and can be dropped from the data set.<BR><BR>
        <LI>The index variable is always incremented by one value beyond =
the=20
        stop value unless you terminate the DO loop in some other=20
manner.<BR><BR>
        <LI>It's easier to manage nested DO loops if you indent the =
statements=20
        in each loop.=20
</LI></UL></TD></TR></TBODY></TABLE><!-- InstanceEndEditable =
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