nlmePredict_PS {mnreadR}

Estimation of the print size value necessary to achieve a given reading speed.

Description

This function uses results from the NLME model created with nlmeModel to estimate the print size value required to achieve a specific reading speed.

Usage

nlmePredict_PS(nlme.model, reading.speed)

Arguments

nlme.model

The object returned by nlmeModel

reading.speed

A specific value of reading speed in words/minute

Value

The function returns a dataframe with a with two variables:

• "reading_speed" -> the reading speed value passed to the function (in words/min)

• "required_print_size" -> the print size required to achieve the reading speed value passed to the function (in logMAR)

Notes

The values of print size returned have been corrected for non-standard testing viewing distance.

For more details on the nlme fit, see:\ Cheung SH, Kallie CS, Legge GE, Cheong AM. Nonlinear mixed-effects modeling of MNREAD data. Invest Ophthalmol Vis Sci. 2008;49:828–835. doi: 10.1167/iovs.07-0555.

See Also

nlmeModel to fit MNREAD data using a nonlinear mixed-effect (NLME) modeling

nlmeParam to estimate Maximum Reading Speed (MRS) and Critical Print Size (CPS) from the NLME model

nlmeCurve to plot the individual MNREAD curves estimated from the NLME model

Examples

# inspect the structure of the dataframe
head(data_low_vision, 10)

#------

# restrict dataset to one MNREAD test per subject (regular polarity only)
data_regular <- data_low_vision %>%
    filter (polarity == "regular")

# run the NLME model for data grouped by subject
 nlme_model <- nlmeModel(data_regular, ps, vd, rt, err, subject) 

#------

# extract the critical print size required 
# to achieve 40 words/min (ie. spot reading) according to the NLME fit 
 nlmePredict_PS(nlme_model, 40) 

#------

# extract the critical print size required 
# to achieve 80 words/min (ie. fluent reading) according to the NLME fit 
 nlmePredict_PS(nlme_model, 80)