fnScoreHist: Histogram of student assessment scores with optional boxplot...

Description Usage Arguments Value Author(s) Examples

Description

fnScoreHist creates a histogram of scores. Optional arguments permit a boxplot to be drawn above the histogram and the plot background to be shaded according to supplied grade boundaries.

The output from fnScoreHist is a ggplot object which can then be saved or customised as needed.

See Examples for more details.

Usage

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fnScoreHist(x,lo=0,hi=100,gradeScheme="",gradeBounds=c(),main="",ylab="Frequency (N students)",addBox=TRUE,pcScore=TRUE)

Arguments

x

A vector of assessment scores (usually percentages but may exceed 100 or be negative).

lo

Minimum value for plotting the x axis, best given as an appropriate multiple of 10 because the axis labels are spaced in tens. If min(x)<lo then lo is adjusted downwards (in multiples of 10)

hi

Maximum value for plotting the x axis, If max(x)>hi then hi is adjusted upwards (in multiples of 10)

gradeScheme

A character string giving the first letter of the grades, ordered from lowest to highest. e.g. "UBSE" or "FP". Letters other than U, B, S, E, F or P will be displayed but not shaded. If gradeScheme is not specified then the background will be unshaded

gradeBounds

A numeric vector of grade thresholds. e.g. c(40,50,60). NOTE: length(gradeBounds) must equal nchar(gradeScheme) - 1, otherwise the background will be unshaded

main

Title for the plot, if required.

ylab

Label for the y axis.

addBox

If TRUE (the default) adds a boxplot with mean point above the histogram.

pcScore

If TRUE (the default) changes the x axis label from "Score" to "Score (%)".

Value

A ggplot object which can be saved or customised as needed.

Author(s)

Martin Roberts, e:psychometrics@plymouth.ac.uk

Examples

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# fnScoreHist Help file
	library("ggplot2")
	library("psychometricsPSMD")
	?fnScoreHist

# Basic Usage (examples employ randomly generated data so the resulting plots are variable)
	fnScoreHist(x=rnorm(86,30,10),lo=-10,hi=80,gradeScheme="UBSE",gradeBounds=c(20,30,45))

# Ability to accommodate NA values and to adjust lo and hi (set to 0 and 80 in this example) to fit data
	fnScoreHist(x=c(-1,2,rnorm(86,30,10),65,93,100,NA),lo=0,hi=80,gradeScheme="USE",gradeBounds=c(18.25,25.62))
 
# If length(gradeBounds) not equal to nchar(gradeScheme) - 1 then no background shading is carried out
	fnScoreHist(x=rnorm(86,30,10),gradeScheme="FP",gradeBounds=c(18.25,25.62))
	
# Scores need not be percentages and the boxplot can be removed
	fnScoreHist(x=rnorm(86,150,20),lo=100,hi=200,gradeScheme="FP",gradeBounds=c(135),addBox=FALSE,pcScore=FALSE)

# Grade boundaries falling outside the lo-hi interval will cause the shading and grade labelling to fail
	fnScoreHist(x=rnorm(86,150,20),lo=100,hi=200,gradeScheme="US",gradeBounds=c(55),pcScore=FALSE)
	fnScoreHist(x=rnorm(86,150,20),lo=50,hi=200,gradeScheme="US",gradeBounds=c(55),pcScore=FALSE)

# Outputs a ggplot object, which can them be editted as necessary.
	plotExample<-fnScoreHist(x=rnorm(86,50,15),gradeScheme="FP",gradeBounds=c(44))
	plotExample  # plot output
	plotExample+ggtitle("Example Distribution of Assessment Scores") # edits

PSMD-Psychometrics/-old-psychometricsPSMD-old- documentation built on May 30, 2019, 4:19 p.m.