m01 - basic concepts summary.mht

sas的考试样题

      onmouseover=3D"window.status=3D'Display details on processing SAS =
programs.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_7.htm">submit a =
SAS=20
      program</A>, SAS reads SAS statements and checks them for errors. =
When it=20
      encounters a subsequent DATA, PROC, RUN, or QUIT statement, SAS =
executes=20
      the previous step in the program.=20
      <P>Each time a step is executed, SAS <A=20
      onmouseover=3D"window.status=3D'Display details on log messages.'; =
"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_7.htm#log">generates a =

      log</A> of the processing activities and the results of the =
processing.=20
      The SAS log collects messages about the processing of SAS programs =
and=20
      about any errors that occur. </P>
      <P>The <A onmouseover=3D"window.status=3D'Display details on log =
messages.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_9.htm">results =
of=20
      processing</A> may vary. Some SAS programs open an interactive =
window or=20
      invoke procedures that create output in the form of a report. =
Other SAS=20
      programs perform tasks such as sorting and managing data, which =
have no=20
      visible results other than messages in the log.=20
</P></TD></TR></TBODY></TABLE><BR></CENTER>
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    <TD><STRONG>SAS Libraries</STRONG><BR>Every SAS file is stored in a =
<A=20
      onmouseover=3D"window.status=3D'Display details on SAS data =
libraries.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_12.htm">SAS =
library</A>,=20
      which is a collection of SAS files such as SAS data sets and =
catalogs. In=20
      some operating environments, a SAS library is a physical =
collection of=20
      files. In others, the files are only logically related. In the =
Windows and=20
      UNIX environments, a SAS library is typically a group of SAS files =
in the=20
      same folder or directory.</TD></TR></TBODY></TABLE><BR></CENTER>
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    <TD>Depending on the libref you use, you can <A=20
      onmouseover=3D"window.status=3D'Display details on storing SAS =
files.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_14.htm">store =
SAS=20
      files</A> in temporary SAS libraries or in permanent SAS =
libraries.=20
      <UL>
        <LI><A=20
        onmouseover=3D"window.status=3D'Display details on storing SAS =
files.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_14.htm#temporary">Tempo=
rary=20
        SAS files</A> that are created during the session are held in a =
special=20
        work space that is assigned the default libref =
<STRONG>Work</STRONG>. If=20
        you don't specify a libref when you create a file (or if you =
specify=20
        <STRONG>Work</STRONG>), the file is stored in the temporary SAS =
library.=20
        When you end the session, the temporary library is deleted. =
<BR><BR>
        <LI><A=20
        onmouseover=3D"window.status=3D'Display details on storing SAS =
files.'; "=20
        onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
        =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_14.htm#permanent">To=20
        store files permanently</A> in a SAS library, you assign it a =
libref=20
        other than the default <STRONG>Work</STRONG>. For example, by =
assigning=20
        the libref <STRONG>Clinic</STRONG> to a SAS library, you specify =
that=20
        files within the library are to be stored until you delete them. =

    </LI></UL></TD></TR></TBODY></TABLE><BR>
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    <TD><STRONG>Referencing SAS Files</STRONG><BR>To reference a SAS =
file, you=20
      use a <A=20
      onmouseover=3D"window.status=3D'Display details on referencing SAS =
files.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_17.htm">two-level=20
      name</A>, <EM><STRONG>libref.filename</STRONG></EM>. In the =
two-level=20
      name, <EM>libref</EM> is the name for the SAS library that =
contains the=20
      file, and <EM>filename</EM> is the name of the file itself. A =
period=20
      separates the libref and filename.=20
      <P>To reference temporary SAS files, you specify the default =
libref=20
      <STRONG>Work</STRONG>, a period, and the filename. Alternatively,=20
      you&nbsp;can simply use a one-level name (the filename only) to =
reference=20
      a file in a temporary SAS library. Referencing a SAS file in any =
library=20
      <STRONG>except Work</STRONG> indicates that the SAS file is stored =

      permanently.=20
      <P>SAS data sets names can be 1 to 32 characters long, must begin =
with a=20
      letter (A-Z, either uppercase or lowercase) or an underscore (_), =
and can=20
      continue with any combination of numbers, letters, or underscores. =

  </P></TD></TR></TBODY></TABLE><BR></CENTER>
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    <TD><STRONG>SAS Data Sets</STRONG><BR>For many of the data =
processing=20
      tasks that you perform with SAS, you access data in the form of a =
<A=20
      onmouseover=3D"window.status=3D'Display details on SAS data =
sets.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_22.htm">SAS data =
set</A>=20
      and use SAS programs to analyze, manage, or present the data.=20
      Conceptually, a SAS data set is a file that consists of two parts: =
a=20
      descriptor portion and a data portion. Some SAS data sets also =
contain one=20
      or more indexes, which enable SAS to locate records in the data =
set more=20
      efficiently.=20
      <P>The <A=20
      onmouseover=3D"window.status=3D'Display details on the descriptor =
portion of SAS data sets.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_23.htm">descriptor=20
      portion</A> of a SAS data set contains information about the data =
set.=20
      <P>The <A=20
      onmouseover=3D"window.status=3D'Display details on the data =
portion of SAS data sets.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_24.htm#Data">data=20
      portion</A> of a SAS data set is a collection of data values that =
are=20
      arranged in a rectangular table. <A=20
      onmouseover=3D"window.status=3D'Display details on rows in SAS =
data sets.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_24.htm#obs">Observation=
s</A>=20
      in the data set correspond to rows or data lines in a raw data =
file or in=20
      an external database. An observation is the information about each =
object=20
      in a SAS data set. <A=20
      onmouseover=3D"window.status=3D'Display details on columns in SAS =
data sets.'; "=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_24.htm#variables">Varia=
bles</A>=20
      in the data set correspond to columns in a raw data file or in an =
external=20
      database. A variable is the set of data values that describes a =
particular=20
      characteristic. If a data value is unknown for a particular =
observation, a=20
      <A=20
      onmouseover=3D"window.status=3D'Display details on missing values =
in SAS data sets.'"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_24.htm#Missval">missing=
=20
      value</A> is recorded in the SAS data set.=20
</P></TD></TR></TBODY></TABLE><BR></CENTER>
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    <TD><STRONG>Variable Attributes</STRONG><BR>In addition to general=20
      information about the data set, the descriptor portion contains <A =

      onmouseover=3D"window.status=3D'Display details on the name =
attribute for variables.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_27.htm">attribute=20
      information</A> for each variable in the data set. The attribute=20
      information includes the variable's <A=20
      onmouseover=3D"window.status=3D'Display details on the name =
attribute for variables.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_28.htm#name">name</A>, =
<A=20
      onmouseover=3D"window.status=3D'Display details on the type =
attribute for variables.';"=20
      onclick=3DsuggestBack() onmouseout=3D"window.status=3D''"=20
      =
href=3D"http://www.sas.com/apps/OLTRN/59080/m1/m1_28.htm#type">type</A>, =
and=20
      <A=20
      onmouseover=3D"window.status=3D'Display details on the length =
attribute for variables.'; "=20