Grade

Description

Binary Grading functions for R.

Details

Index:

\link{grade.discreteprobability}
                        Grade Discrete Probability Sets
\link{grade.interval}          Grade Intervals
\link{grade.isscalar}          Check if an object is a scalar
\link{grade.negative}          Check the Sign of a Number
\link{grade.number}            Grade Single Numbers
\link{grade.orderedset}        Grade Ordered Sets
\link{grade.parse}             Parse input
\link{grade.parsechunk}
\link{grade.parseset}
\link{grade.set}               Grade Sets
\link{grade.truefalse}         True/False answers

Note

There are some common arguments across all of the grade functions. These are:

• correctansInput to be the correct answer. May be a string or a vector. Checks are likely to be more stringent on this component and result in more errors. E.g. grade.interval requires that correctans have length 2.

• studentansInput to check for correctness. May be a string or a vector. Most of the grade functions check it against correctans

• useevalTRUE or FALSE. If TRUE eval is used to evaluate text elements. If FALSE as.numeric is used to evaluate text elements. The advantage of using eval is more forgiveness for input, e.g. eval of "pi" returns 3.1415, or eval of "1/2" returns 0.5, but as.numeric returns NA in each case. The disadvantage is that eval could be abused to run arbitrary code leading to a security issue. However, the grade package does not submit any text to either eval or as.numeric that contains any of the characters '[', ']', '(', ')', '<', '>', '=' or ','. It is unlikely that code containing function calls could be inserted. So useeval defaults to TRUE. If there are problems, or you are worried, you can always set useeval=FALSE.

• usenaTRUE or FALSE. If TRUE, NA is considered to be a valid number. If FALSE, NA is considered to be invalid. Default is usena=FALSE.

• useinfTRUE or FALSE. If TRUE, Inf and -Inf are considered to be valid numbers. If FALSE, Inf and -Inf are considered to be invalid. Default is useinf=FALSE.

• quietTRUE or FALSE. If FALSE, errors or bad input result in more warning messages. Default is quiet=TRUE.

Author(s)

Leif Johnson <leif.t.johnson@gmail.com>

Maintainer: Leif Johnson <leif.t.johnson@gmail.com>

References

http://www.stat.umn.edu/~leif/software/grade

Grade Discrete Probability Sets

Description

Checks a students probability distribution, makes sure that (1) It sums to 1 (2) All elements are >= 0

Optionally, it compares the students to a correct one. Order is optionally enforced.

Usage

grade.discreteprobability(correctans, studentans, tolerance=.01,
                          useeval=TRUE, usena=FALSE, useinf=FALSE,
                          quiet=TRUE, ordered=FALSE, checkcorrect=TRUE)

Arguments

Details

If checkcorrect=FALSE, grade.discreteprobability does not do any checks on correctans. In this case to be correct, studentans needs to satisfy discrete probability constraints – all elements >= 0 and sums to 1.

If checkcorrect=TRUE discrete probability constraints are enforced on correctans. studentans needs to match correctans in this case. Order is only enforced if ordered=TRUE.

grade.discreteprobability does not use NA. If usena=TRUE grade.discreteprobability sets it to FALSE and issues a warning message.

Value

TRUE or FALSE indicating match success or failure respectively. FALSE is also returned if studentans does not look like a set.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.set

Examples

# TRUE
grade.discreteprobability(c(1/2,1/2), "[.5, .5]")
# TRUE
grade.discreteprobability(NULL, "[0, .33, .17, .5]", checkcorrect=FALSE) 

# FALSE
grade.discreteprobability(NULL, "[-1, 0, 0, 1, 1]", checkcorrect=FALSE)

# TRUE
grade.discreteprobability(c(0, 1/2, 1/4, 1/4), "[0, 1/2, 1/4, 1/4]")
# FALSE
grade.discreteprobability(c(0, 1/2, 1/4, 1/4), "[0, .25, .25, .5]",
                          ordered=TRUE)

# TRUE
grade.discreteprobability(c(0, 1/2, 1/4, 1/4), "[0, .5, .25, .25]",
                          ordered=TRUE)

Grade Intervals

Description

Checks a students interval against a correct one.

Usage

grade.interval(correctans, studentans, tolerance=0.01, useeval=TRUE, 
               usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Details

usena is ignored in this function. If set to true, grade.interval sets it back to false and produces a warning message. grade.interval expects correctans to be a vector of length 2, if not it errors out. If correctans is in reverse order and quiet=FALSE, grade.interval issues a warning, but continues grading.

Value

TRUE or FALSE indicating match success or failure respectively. FALSE is also returned if studentans does not look like an interval.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.set grade.number

Examples

grade.interval(c(1,2), "[1,2]") # TRUE
grade.interval(c(1,2), "[1.1,2]", tolerance=".01") # FALSE

grade.interval(c(1,pi), "(1,3.142)", tolerance=".001") # TRUE

Check the Sign of a Number

Description

Sees if studentans is negative, correctans is ignored.

Usage

grade.negative(correctans=NULL, studentans, tolerance=0.01,
               useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Value

TRUE if (studentans < -tolerance) FALSE otherwise.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.set grade.number

Examples

grade.negative(studentans=0, "1") # FALSE
grade.negative(NULL, "1.1", tolerance=".01") # FALSE

grade.negative("soup", "-.1", tolerance=.05) # TRUE

Grade Single Numbers

Description

Checks studentans against correctans. For scalars only.

Usage

grade.number(correctans, studentans, tolerance=0.01,
             useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Value

TRUE if studentans is within tolerance of correctans. FALSE otherwise.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.set grade.negative

Examples

grade.number(1, "1") # TRUE
grade.number(1, "1.1", tolerance=".01") # FALSE

grade.number(pi, "3.142", tolerance=".001") # TRUE

grade.number(1, "[1]") # TRUE

Parse Input

Description

Parse input, returning either NULL or a vector of the values.

Usage

grade.isscalar(x, usena=FALSE, useinf=FALSE, quiet=TRUE)

grade.parse(ans, useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)
grade.parseset(ans, useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)
grade.parsechunk(ans, useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Details

grade.isscalar checks to see if x is a finite numeric scalar (vector of length 1). If usena=TRUE, NA is also accepted. If useinf=TRUE, Inf and -Inf are also accepted.

Input to the grade.parse functions can be a string or a vector. grade.parsechunk will only return scalars, the other two will return a vector. All three check return values using grade.isscalar on each element.

grade.parse delegates character types to either grade.parsechunk or grade.parseset. If the string contains any of the characters '[', ']', '(', ')', or ',' the string is sent to grade.parseset. Otherwise it is sent to grade.parsechunk.

If x is a character, grade.parsechunk checks for any of the forbidden characters '[', ']', '(', ')', or ','. If any are found grade.parsechunk refuses to evaluate the string.

If x is a character, grade.parsechunk makes sure that it looks like a vector or set. I.e. it starts with an open bracket or parenthesis and ends with a close bracket or parenthesis. No other brackets or parenthesis are allowed. The middle is expected to be a comma delimited list. See the examples for more clarification.

If useeval=TRUE, text elements are evaluated using eval. If useeval=FALSE text elements are coerced using as.numeric. eval is more forgiving to input, i.e. eval of text input '1/2' returns .25, but as.numeric of text '1/2' returns NA. However, eval does leave an opening for unchecked code to be run in R. Text containing parenthesis or brackets is not put into either eval or as.numeric by the grade.parse functions, but there is still a risk. If you are concerned, set useeval=FALSE.

Value

grade.parse and grade.parseset returns either a vector of the values, or NULL if the input was not valid.

grade.parsechunk returns either a single value, or NULL if the input was not valid.

grade.isscalar returns TRUE if x is a scalar (vector of length 1), FALSE otherwise.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.set grade.number

Examples

grade.parse("[1, 2, 3]") # returns c(1,2,3)
grade.parse("[NA, 1, 2]") # returns NULL
grade.parse("[NA, 1, 2]", usena=TRUE) # returns c(NA, 1, 2)
grade.parse("[pi]") # returns 3.141....
grade.parse("[pi]", useeval=FALSE) # returns NULL

grade.parsechunk("1") # 1
grade.parsechunk(",1") # NULL
grade.parsechunk("[1]", quiet=FALSE) # NULL, with error message

grade.parseset("[1,2,3]") # c(1,2,3)

grade.isscalar(1) # TRUE
grade.isscalar(c(1,2)) # FALSE
grade.isscalar(NA) # FALSE
grade.isscalar(NA, usena=TRUE) # TRUE
grade.isscalar(Inf) # FALSE
grade.isscalar(Inf, useinf=TRUE) # TRUE

Grade Sets

Description

Checks a the set (vector in R) studentans against correctans. grade.orderedset enforces order, grade.set does not.

Usage

grade.set(correctans, studentans, tolerance=0.01, useeval=TRUE,
          usena=FALSE, useinf=FALSE, quiet=TRUE)
grade.orderedset(correctans, studentans, tolerance=0.01, useeval=TRUE, 
                 usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Value

TRUE if the sets match. FALSE otherwise.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet.

See Also

grade grade.number

Examples

grade.set(c(1,2), "[1,2]") # TRUE
grade.orderedset(c(1,2), "[1,2]") # TRUE

grade.set(c(2,1), "[1,2]") # TRUE
grade.orderedset(c(2,1), "[1,2]") # FALSE

grade.set(c(1,2), "[1.1,2]", tolerance=".01") # FALSE

grade.set(c(1,2,3,4,5), "(5,4,3,2,1)") # TRUE
grade.set(c(1,2,3,4,5), "(5,4,3,2)") # FALSE

grade.orderedset("[NA, 1, 2]", c(NA, 1, 2)) #FALSE, usena=F
grade.orderedset("[NA, 1, 2]", c(NA, 1, 2), quiet=FALSE) # FALSE, but with warning
grade.orderedset("[NA, 1, 2]", c(NA, 1, 2), usena=TRUE) # TRUE

Grade True False Answers

Description

Checks studentans against correctans. For true/false answers only.

Usage

grade.truefalse(correctans, studentans, tolerance=0.01,
             useeval=TRUE, usena=FALSE, useinf=FALSE, quiet=TRUE)

Arguments

Value

TRUE if studentans==correctans AND both studentans and correctans are TRUE or FALSE. FALSE otherwise.

Note

The grade main page contains a discussion of the common parameters correctans, studentans, useeval, usena, useinf, quiet. grade.truefalse does not accept usena or useinf. Setting usena=TRUE or useinf=TRUE will result in a warning. tolerance is not used in grade.truefalse. These arguments are included for compatibility with the other function calls in grade.

See Also

grade

Examples

grade.truefalse(TRUE, TRUE) # TRUE
grade.truefalse(TRUE, "TRUE") # TRUE
grade.truefalse("FALSE", "TRUE") # FALSE
## depending on your environment settings, this next example may work.
#grade.truefalse("F", F) # TRUE if your environment has not redefined 'F'