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Empty (Void) Elements

When analyzing real-world data, you might not always have a complete data set. TI‑Nspire™ CAS Software allows empty, or void, data elements so you can proceed with the nearly complete data rather than having to start over or discard the incomplete cases.

You can find an example of data involving empty elements in the Lists & Spreadsheet chapter, under “Graphing spreadsheet data.”

The delVoid() function lets you remove empty elements from a list. The isVoid() function lets you test for an empty element. For details, see delVoid(), here, and isVoid(), here.

Note: To enter an empty element manually in a math expression, type “_” or the keyword void. The keyword void is automatically converted to a “_” symbol when the expression is evaluated. To type “_” on the handheld, press / _.

Calculations involving void elements
The majority of calculations involving a void input will produce a void result. See special cases below.

List arguments containing void elements
The following functions and commands ignore (skip) void elements found in list arguments. count, countIf, cumulativeSum, freqTable►list, frequency, max, mean, median, product, stDevPop, stDevSamp, sum, sumIf, varPop, and varSamp, as well as regression calculations, OneVar, TwoVar, and FiveNumSummary statistics, confidence intervals, and stat tests
SortA and SortD move all void elements within the first argument to the bottom.
In regressions, a void in an X or Y list introduces a void for the corresponding element of the residual.
An omitted category in regressions introduces a void for the corresponding element of the residual.
A frequency of 0 in regressions introduces a void for the corresponding element of the residual.

List arguments containing void elements

The following functions and commands ignore (skip) void elements found in list arguments.

count, countIf, cumulativeSum, freqTable►list, frequency, max, mean, median, product, stDevPop, stDevSamp, sum, sumIf, varPop, and varSamp, as well as regression calculations, OneVar, TwoVar, and FiveNumSummary statistics, confidence intervals, and stat tests

SortA and SortD move all void elements within the first argument to the bottom.

In regressions, a void in an X or Y list introduces a void for the corresponding element of the residual.

An omitted category in regressions introduces a void for the corresponding element of the residual.

A frequency of 0 in regressions introduces a void for the corresponding element of the residual.