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<title>ploticus: proc usedata</title>
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  <td><br><h2>proc usedata</h2></td>
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  Version 2.33 Jun'06
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.TH proc_usedata PL "02-JUN-2006   PL ploticus.sourceforge.net"
 
.LP
\fBproc usedata\fR may be used to select the 
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\0current data set
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for plotting
when more than one data set resides in memory.
Additional in-memory data sets can be generated, for instance, by 
\fBproc processdata\fR.
.LP
Ploticus accomodates multiple in-memory data sets using a stack mechanism.
Stack elements are identified by number.
When a data set is read using \fBproc getdata\fR the resulting data becomes element 0.
If \fBproc tabulate\fR or \fBproc processdata\fR are invoked to derive data,
the result becomes element 1.
If another \fBproc tabulate\fR or \fBproc processdata\fR is applied to element 1, the
result becomes element 2.  And so on.
.LP
Normally the current data set 
for plotting is always the result of the most recent \fBgetdata\fR, \fBprocessdata\fR, or \fBtabulate\fR.
\fBproc usedata\fR is used on those occasions
where it is necessary to get back to the original data set, or access a data set that is lower on the stack.

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.SH Notes
\fBproc getdata\fR always clears the stack before filling element 0.
.LP
The old \fBproc originaldata\fR now maps to this proc, equivalent to \fCoriginal: yes\fR.

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.SH Attributes
.LP
If no attributes are specified, the default action is \fCoriginal: yes\fR

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.LP
\fBoriginal\fR  
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\fCyes\fR
.IP \0
The data most recently read by \fBproc getdata\fR 
becomes the current data set for plotting.

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.LP
\fBelement\fR  
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&nbsp; &nbsp;
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\fIn\fR
.IP \0
Element \fIn\fR becomes the current data set for plotting.

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.LP
\fBpop\fR  
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\fIn\fR
.IP \0
\fIn\fR elements are popped from the stack to arrive at the current data set for plotting.

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.LP
\fBfieldnames\fR 
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&nbsp; &nbsp;
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\fInamelist\fR
.IP \0
Set any data field names that will be in effect.
Field names are not retained in the data set stack structure,
so if a data set that had field names is made the current data set,
the field names must be respecified here using this attribute.

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.SH Example
.LP
.nf
 \0 #proc usedata
 \0   original: yes
.fi

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