`<extractMath>`

Extracts a sub-expression from a math expression by name or index

<extractMath> is a General Operator component that extracts data from mathematical expressions. (See also, the <matchesPattern> component for an alternative method for extracting data.)

The types of data that can be extracted with <extractMath> are:

the number of operands in the expression
the individual operands themselves
the functions involved in an expression
the function arguments

Attributes and Properties

Attributes for `<extractMath>`

Highlighted (3)

displayDigits

integer. Default value: 3. Number of significant digits to display when rendering this number.

format

keyword. Input format.

Value	Description
`text` (default)	Plain-text math notation (e.g., `x^2 + 1`).
`latex`	LaTeX-formatted math (e.g., `x^{2} + 1`).

simplify

keyword. Level of simplification applied to the expression.

Value	Description
`none` (default)	No simplification is applied.
`full`	Fully simplify the expression.
`numbers`	Simplify numeric subexpressions only, leaving symbolic structure intact.
`numbersPreserveOrder`	Like `numbers`, but does not reorder commutative operands.
`normalizeOrder`	Reorder commutative operands into a canonical form without simplifying values.

Number display (5)

avoidScientificNotation

boolean. Default value: false. Whether to render numbers in full decimal form rather than scientific notation.

displayDecimals

integer. Default value: 2. Number of decimal places to display when rendering this number.

displayDigits

integer. Default value: 3. Number of significant digits to display when rendering this number.

displaySmallAsZero

number. Default value: 1e-14. Threshold below which numbers are displayed as zero.

padZeros

boolean. Default value: false. Whether to pad displayed numbers with trailing zeros to fill the requested digits/decimals.

Positioning (2)

anchor

point. Default value: $\left( 0, 0 \right)$. Coordinates of the anchor point used to position this component on a graph.

positionFromAnchor

keyword. Where this component sits relative to its anchor point.

Value	Description
`upperRight`	Place the component above and to the right of the anchor point.
`upperLeft`	Place the component above and to the left of the anchor point.
`lowerRight`	Place the component below and to the right of the anchor point.
`lowerLeft`	Place the component below and to the left of the anchor point.
`top`	Place the component directly above the anchor point.
`bottom`	Place the component directly below the anchor point.
`left`	Place the component directly to the left of the anchor point.
`right`	Place the component directly to the right of the anchor point.
`center` (default)	Center the component on the anchor point.

Other (16)

argumentNumber

number. 1-based index of the argument to extract.

assumptions

math. Default value: $＿$. Assumptions applied when simplifying or comparing.

createIntervals

boolean. Default value: false. Whether range expressions are interpreted as intervals.

createVectors

boolean. Default value: false. Whether tuple-like expressions are interpreted as vectors.

displayBlanks

boolean. Default value: true. Whether blanks (placeholders) are visibly rendered.

draggable

boolean. Default value: true. Whether the math component can be dragged on a graph.

expand

boolean. Default value: false. Whether to expand the expression.

functionSymbols

textList. Default value: ["f","g"]. Symbols treated as function names when parsing.

layer

number. Default value: 0. Z-order layer index when shown on a graph.

operandNumber

number. 1-based index of the operand to extract.

parseScientificNotation

boolean. Default value: false. Whether to parse expressions like 1e3 as scientific notation.

referencesAreFunctionSymbols

reference. References whose names should be treated as function symbols when parsing.

renderMode

text. Default value: inline. How the math is rendered (e.g. "inline", "display").

splitSymbols

boolean. Default value: true. Whether multi-character symbols are split into a product of variables.

type

keyword. What kind of sub-expression to extract.

Value	Description
`operand`	Extract a single operand of the top-level operation.
`function`	Extract the function being applied (for a function call).
`functionArgument`	Extract an argument of the function being called.
`numOperands`	Extract the count of operands at the top level.
`recursiveOperands`	Extract all operands found recursively through nested operations.

unordered

boolean. Default value: false. Whether tuple- or list-like math expressions should be treated as unordered for comparison.

Common to all components (9)

copy

reference. Create an independent copy of another component by reference. Enter a references a $name.

disabled

boolean. Default value: false. Whether this component is disabled and cannot be interacted with.

extend

reference. Extend another component by reference, inheriting its children and attributes. Enter a reference as $name.

fixed

boolean. Default value: false. Whether this component's value is fixed and cannot be modified.

fixLocation

boolean. Default value: false. Whether this component's location is fixed (preventing it from being moved while still allowing other modifications).

hide

boolean. Default value: false. Whether to hide this component from the rendered output.

isResponse

boolean. Default value: false. Whether this component is treated as a response for the purposes of assessment.

name

text. The name used to reference this component from elsewhere in the document.

styleNumber

integer. Default value: 1. The style number used to select this component's visual styling from the available style definitions.

Properties for `<extractMath name="e">`

Highlighted (3)

$e.displayDigits

integer. Number of significant digits to display when rendering this number.

$e.format

text. Input format.

$e.simplify

text. Level of simplification applied to the expression.

Number display (5)

$e.avoidScientificNotation

boolean. Whether to render numbers in full decimal form rather than scientific notation.

$e.displayDecimals

integer. Number of decimal places to display when rendering this number.

$e.displayDigits

integer. Number of significant digits to display when rendering this number.

$e.displaySmallAsZero

number. Threshold below which numbers are displayed as zero.

$e.padZeros

boolean. Whether to pad displayed numbers with trailing zeros to fill the requested digits/decimals.

Positioning (2)

$e.anchor

point. The coordinates where this component is anchored on the graph.

$e.positionFromAnchor

text. Where this component sits relative to its anchor point.

Other (40)

$e.argumentNumber

number. 1-based index of the argument to extract.

$e.assumptions

math. Assumptions applied when simplifying or comparing.

$e.backgroundColor

text. Human-readable name for this component's background color, derived from the active style and theme.

$e.columns

[ math ]. The matrix's entries grouped by column.

$e.createIntervals

boolean. Whether range expressions are interpreted as intervals.

$e.createVectors

boolean. Whether tuple-like expressions are interpreted as vectors.

$e.disabled

boolean. Whether this component is disabled and cannot be interacted with.

$e.displayBlanks

boolean. Whether blanks (placeholders) are visibly rendered.

$e.draggable

boolean. Whether the math component can be dragged on a graph.

$e.expand

boolean. Whether to expand the expression.

$e.fixed

boolean. Whether this component's value is fixed and cannot be modified.

$e.fixLocation

boolean. Whether this component's location is fixed (preventing it from being moved while still allowing other modifications).

$e.functionSymbols

textList. Symbols treated as function names when parsing.

$e.hidden

boolean. Whether this component is hidden from the rendered output.

$e.isNumber

boolean. Whether the expression evaluates to a finite number.

$e.isNumeric

boolean. Whether the expression evaluates to any number (including infinities).

$e.latex

latex. The expression rendered as a LaTeX string.

$e.layer

number. Z-order layer index when shown on a graph.

$e.list

[ math ]. The math expression interpreted as a list (its elements).

$e.matrix

[ math ]. The math expression interpreted as a matrix (its entries by row and column).

$e.matrixSize

numberList. The size of the math expression as a matrix, as a [numRows, numColumns] list.

$e.number

number. The numeric value of the expression (NaN if not a number).

$e.numColumns

integer. The number of columns when the math expression is interpreted as a matrix.

$e.numDimensions

integer. The number of dimensions if the math expression is interpreted as a vector or matrix.

$e.numListItems

integer. The number of items when the math expression is interpreted as a list.

$e.numRows

integer. The number of rows when the math expression is interpreted as a matrix.

$e.operandNumber

number. 1-based index of the operand to extract.

$e.parseScientificNotation

boolean. Whether to parse expressions like 1e3 as scientific notation.

$e.renderMode

text. How the math is rendered (e.g. "inline", "display").

$e.rows

[ math ]. The matrix's entries grouped by row.

$e.splitSymbols

boolean. Whether multi-character symbols are split into a product of variables.

$e.text

text. The expression rendered as a plain text string.

$e.textColor

text. Human-readable name for this component's text color, derived from the active style and theme.

$e.textStyleDescription

text. Human-readable description of this component's text styling (color and any background color).

$e.unordered

boolean. Whether list-like values are treated as unordered.

$e.value

extractMath. The math expression value.

$e.vector

[ math ]. The math expression interpreted as a vector (its components).

$e.x

math. The first component of the math expression when interpreted as a vector.

$e.y

math. The second component of the math expression when interpreted as a vector.

$e.z

math. The third component of the math expression when interpreted as a vector.

Common to all components (4)

$e.doenetML

text. The DoenetML source code that produced this component.

$e.hide

boolean. Whether to hide this component from the rendered output.

$e.isResponse

boolean. Whether this component is treated as a response for the purposes of assessment.

$e.styleNumber

integer. The style number used to select this component's visual styling from the available style definitions.

Examples

Example: Extracting operands and number of operands

To extract an operand, you must also specify the operandNumber.

Example: Extracting functions and function arguments

To extract a function or functionArgument, you must first extract the operand under consideration. In order to extract an individual functionArgument in the case of a multivariable function; the argumentNumber must be provided as well.

Note that Doenet recognizes $f$ and $g$ as function symbols by default. If other symbols are to represent functions, they can be defined within the <math> component using the functionSymbols attribute.

Attribute Examples

Attribute Example: type

The type attribute specifies the value to be extracted; it takes one of four possible inputs: operand, numOperands, function, and functionArgument.

Attribute Example: operandNumber

The operandNumber attribute is necessary when the operand type is extracted. It specifies the location of the requested operand within the expression.

Attribute Example: argumentNumber

When function arguments are extracted from a math expression, the argumentNumber attribute specifies the location of the requested argument.

exercises extractMathOperator

<extractMath>