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<H2><A NAME="SECTION00633000000000000000"> </A><A NAME="1519"> </A><A NAME="1520"> </A>
<BR>
Specifying Elements in a Table
</H2>
<P>
The MIDAS table file system is described in detail in chapter 5 of this
volume. Here we just explain briefly how to access the various elements
in a table file. To do so, it is
necessary to specify the <I>table name</I>, the <I>column</I> and
the <I>row</I>. This is done in the following format (order):
<BR>
<TT>table column row</TT>
<BR>
where <BR>
<I>table</I> is the table name;
<BR>
<I>column</I> is the desired column which can be referenced by label as
<TT>:col</TT> or by sequence number as <TT>#n</TT>; <BR>
<I>row</I> is the desired row referenced by number as
<TT>@n</TT> or by a value in a predefined reference column.
<BR>
Like descriptor and keyword names, column labels are case insensitive.
The command:<BLOCKQUOTE>
<TT>READ/TABLE tname #3 @10</TT></BLOCKQUOTE>would display the element in column 3 of row 10 in table file
<TT>tname.tbl</TT> .
<BR>
Similarly, the command:<BLOCKQUOTE>
<TT>READ/TABLE tname :MAGNITUDE 20.0</TT></BLOCKQUOTE>would access the element in the column labeled `MAGNITUDE'
and value 20.0 in the reference column (this reference column must have been
defined before via the <TT>SET/REFCOLNUM</TT> command).
<BR>
Note, that we need not specify the file extension <TT>.tbl</TT>
as in the descriptor related commands.
All table commands default the data files to tables with extension <TT>.tbl</TT>.
<BR>
<BR>
Single table elements can also be written in a more direct way, via
<BR>
<TT>table,column,row = value</TT>,
<BR>
e.g. to set the element in the 3rd row of the
column labeled <TT>:XREF</TT> in the table <TT>lola.tbl</TT> to <TT>1.234</TT>, use <BR>
<TT>lola,:xref,@3 = 1.234</TT>
<BR>
The <I>value</I> can also be an <I>expression</I> made up of constants and elements
of any MIDAS data structure, see the subsection <A HREF="node40.html#symbol-substitution">3.6.2</A>.
<BR>
<BR>
Some of the commands dealing with tables are:
<BR>
<TT>READ/TABLE, WRITE/TABLE, COMPUTE/TABLE, SHOW/TABLE, EDIT/TABLE,
COPY/TABLE</TT>.
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
</ADDRESS>
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