# Matrix entry#

Matrix entry parts ask the student to enter a matrix of numbers. Marks are awarded if every cell in the student’s answer is equal to the corresponding cell in the correct answer, within the allowed margin of error.

## Marking#

The expected answer to the part. This is a JME expression which must evaluate to a matrix.

Number of rows#

The default number of rows in the student’s answer field.

Number of columns#

The default number of columns in the student’s answer field.

Allow student to change size of matrix?#

If this is ticked, then the student can change the number of rows or columns in their answer. Use this if you don’t want to give a hint about the dimensions of the answer.

Minimum number of rows#

If the student is allowed to change the size of the matrix, then the number of rows they choose must be at least this number.

Maximum number of rows#

If the student is allowed to change the size of the matrix, then the number of rows they choose must be at most this number. A value of 0 means there is no limit.

Minimum number of columns#

If the student is allowed to change the size of the matrix, then the number of columns they choose must be at least this number.

Maximum number of columns#

If the student is allowed to change the size of the matrix, then the number of columns they choose must be at most this number. A value of 0 means there is no limit.

Margin of error allowed in each cell#

If the absolute difference between the student’s value for a particular cell and the correct answer’s is less than this value, then it will be marked as correct.

Gain marks for each correct cell?#

If this is ticked, the student will be awarded marks according to the proportion of cells that are marked correctly. If this is not ticked, they will only receive the marks for the part if they get every cell right. If their answer does not have the same dimensions as the correct answer, they are always awarded zero marks.

Precision restriction#

You can insist that the student gives their answer to a particular number of decimal places or significant figures. For example, if you want the answer to be given to 3 decimal places, $$3.1$$ will fail this restriction, while $$3.100$$ will pass.

The cells of the correct answer are rounded off to the maximum precision as the student used in any of their cells, or the required precision - whichever is greater. If the student’s answer is within the specified tolerance of the rounded-off correct value, it is classed as correct. Finally, if any of the cells in the student’s answer are not given to the required precision, the penalty is applied.

If the precision doesn’t matter, select None.

Allow the student to enter fractions?#

This option is only available when no precision restriction is applied, since they apply to decimal numbers. If this is ticked, the student can enter a ratio of two whole numbers, e.g. -3/8, as their answer.

Display numbers in the correct answer as fractions?#

If this is ticked, then non-integer numbers in the correct answer will be displayed as fractions instead of decimals.

Require trailing zeros?#

This option only applies when a precision restriction is selected. If this is ticked, the student must add zeros to the end of their answer (when appropriate) to make it represent the correct precision. For example, consider a part whose correct answer is $$1.4$$, and you want the student’s answer to be correct to three decimal places. If “Require trailing zeros?” is ticked, only the answer $$1.400$$ will be marked correct. If it is not ticked, any of $$1.4$$, $$1.40$$ or $$1.400$$ will be marked as correct. If too many zeros are used, e.g. $$1.4000$$, the answer is marked as incorrect.

Partial credit for wrong precision#

This option only applies when a precision restriction is selected. If the student does not give all of the cells in their answer to the required precision, they only get this much of the available credit for the part.

Message if wrong precision#

This option only applies when a precision restriction is selected. If the student does not give all of the cells in their answer to the required precision, they are given this feedback message.

Pre-filled cells#

A 2D array of either string or number values, giving values to fill the cells of the matrix with. An empty string "" denotes a blank cell that the student can write an answer in; any other value is filled in and the student may not change it.

## Marking settings#

The studentAnswer parameter is a list value, comprising a list of lists of strings. studentAnswer[i][j] is the string that the student typed in the j-th column of the i-th row.

This part type provides the following properties to the settings object:

numRows#

The default Number of rows in the student’s answer.

numColumns#

The default Number of columns in the student’s answer.

allowResize#

Allow student to change size of matrix?

tolerance#

Margin of error allowed in each cell

markPerCell#

Gain marks for each correct cell?

allowFractions

Allow the student to enter fractions?

precisionType

The type of precision restriction to apply: one of "none", "dp" or "sigfig", as set in Precision restriction.

precision

The number of decimal places or significant figures to require.

precisionPC

The proportion of credit to award if any cell is not given to the required precision.

precisionMessage

A message to display in the marking feedback if any cell in the student’s answer was not given to the required precision.

strictPrecision

Require trailing zeros?

## Example#

A question in the Numbas demo demonstrates a variety of ways of using matrix entry parts.

Numbas demo: matrix entry part type