ploticus: proc usedata

## proc usedata | Welcome Gallery Handbook |
| Manual page for proc_usedata(PL)

## Description

proc usedata may be used to select the "current data set" for plotting when more than one data set resides in memory.`` Additional in-memory data sets can be generated, for instance, by proc tabulate or proc processdata.``

Ploticus accomodates multiple in-memory data sets using a stack mechanism.`` Stack elements are identified by number.`` When a data set is read using proc getdata the resulting data becomes element 0.`` If proc tabulate or proc processdata are invoked to derive data, the result becomes element 1.`` If another proc tabulate or proc processdata is applied to element 1, the result becomes element 2. And so on.``

Normally the current data set for plotting is always the result of the most recent getdata, processdata, or tabulate.`` proc usedata 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.``

## Notes

proc getdata always clears the stack before filling element 0.``

The old proc originaldata now maps to this proc, equivalent to `original: yes`.``

## Attributes

If no attributes are specified, the default action is `original: yes`

original `yes`

  The data most recently read by proc getdata becomes the current data set for plotting.``

element n

  Element n becomes the current data set for plotting.``

pop n

  n elements are popped from the stack to arrive at the current data set for plotting.``

## Example

       #proc usedata
         original: yes

data display engine
Copyright Steve Grubb

Markup created by unroff 1.0, `` `` December 10, 2002.